Merge branch 'megatron-lm_dtk24.04' into 'main'

Megatron lm dtk24.04

See merge request OpenDAS/megatron-lm!1

megatron/core/package_info.py

+# Copyright (c) 2023, NVIDIA CORPORATION.  All rights reserved.
+
+
+MAJOR = 0
+MINOR = 3
+PATCH = 0
+PRE_RELEASE = ''
+
+# Use the following formatting: (major, minor, patch, pre-release)
+VERSION = (MAJOR, MINOR, PATCH, PRE_RELEASE)
+
+__shortversion__ = '.'.join(map(str, VERSION[:3]))
+__version__ = '.'.join(map(str, VERSION[:3])) + ''.join(VERSION[3:])
+
+__package_name__ = 'megatron_core'
+__contact_names__ = 'NVIDIA'
+__contact_emails__ = 'nemo-toolkit@nvidia.com'  # use NeMo Email
+__homepage__ = (
+    'https://docs.nvidia.com/deeplearning/nemo/user-guide/docs/en/stable/'  # use NeMo homepage
+)
+__repository_url__ = 'https://github.com/NVIDIA/Megatron-LM/megatron/core'
+__download_url__ = 'https://github.com/NVIDIA/Megatron-LM/releases'
+__description__ = (
+    'Megatron Core - a library for efficient and scalable training of transformer based models'
+)
+__license__ = 'BSD-3'
+__keywords__ = (
+    'deep learning, machine learning, gpu, NLP, NLU, language, transformer, nvidia, pytorch, torch'
+)

megatron/core/parallel_state.py

@@ -2,9 +2,11 @@
 
 """Model and data parallel groups."""
 
-import torch
+import os
 from typing import Optional
 
+import torch
+
 from .utils import GlobalMemoryBuffer
 
 # Intra-layer model parallel group that the current rank belongs to.
@@ -19,6 +21,9 @@ _EMBEDDING_GROUP = None
 _POSITION_EMBEDDING_GROUP = None
 # Data parallel group that the current rank belongs to.
 _DATA_PARALLEL_GROUP = None
+_DATA_PARALLEL_GROUP_GLOO = None
+# FP8 amax reduction group.
+_AMAX_REDUCTION_GROUP = None
 
 _VIRTUAL_PIPELINE_MODEL_PARALLEL_RANK = None
 _VIRTUAL_PIPELINE_MODEL_PARALLEL_WORLD_SIZE = None
@@ -53,9 +58,10 @@ def initialize_model_parallel(
     pipeline_model_parallel_size: int = 1,
     virtual_pipeline_model_parallel_size: Optional[int] = None,
     pipeline_model_parallel_split_rank: Optional[int] = None,
+    use_fp8: bool = False,
+    use_sharp: bool = False,
 ) -> None:
-    """
-    Initialize model data parallel groups.
+    """Initialize model data parallel groups.
 
     Arguments:
         tensor_model_parallel_size (int, default = 1):
@@ -93,6 +99,17 @@ def initialize_model_parallel(
             pipeline_model_parallel_split_rank is 3, then ranks 0-2
             will be the encoder and ranks 3-7 will be the decoder.
 
+        use_fp8 (bool, default = False):
+            Construct GPU groups needed for FP8 training, namely for
+            amax reduction across the product of the data-parallel and
+            tensor-parallel groups.
+
+        use_sharp (bool, default = False):
+            Set the use of SHARP for the collective communications of
+            data-parallel process groups. When `True`, run barrier
+            within each data-parallel process group, which specifies
+            the SHARP application target groups.
+
     Let's say we have a total of 16 GPUs denoted by g0 ... g15 and we
     use 2 GPUs to parallelize the model tensor, and 4 GPUs to parallelize
     the model pipeline. The present function will
@@ -108,6 +125,7 @@ def initialize_model_parallel(
     are on the same DGX box. For example if we are using 2 DGX-1 boxes
     with a total of 16 GPUs, rank 0 to 7 belong to the first box and
     ranks 8 to 15 belong to the second box.
+
     """
     # Get world size and rank. Ensure some consistencies.
     assert torch.distributed.is_initialized()
@@ -119,17 +137,19 @@ def initialize_model_parallel(
             f"({tensor_model_parallel_size}) x pipeline_model_parallel_size ({pipeline_model_parallel_size})"
         )
 
-    data_parallel_size: int = world_size // (tensor_model_parallel_size *
-                                             pipeline_model_parallel_size)
+    data_parallel_size: int = world_size // (
+        tensor_model_parallel_size * pipeline_model_parallel_size
+    )
 
-    num_tensor_model_parallel_groups: int  = world_size // tensor_model_parallel_size
+    num_tensor_model_parallel_groups: int = world_size // tensor_model_parallel_size
     num_pipeline_model_parallel_groups: int = world_size // pipeline_model_parallel_size
     num_data_parallel_groups: int = world_size // data_parallel_size
 
     if virtual_pipeline_model_parallel_size is not None:
         if not pipeline_model_parallel_size > 2:
-            raise RuntimeError("pipeline-model-parallel size should be greater than 2 with "
-                               "interleaved schedule")
+            raise RuntimeError(
+                "pipeline-model-parallel size should be greater than 2 with interleaved schedule"
+            )
         global _VIRTUAL_PIPELINE_MODEL_PARALLEL_RANK
         global _VIRTUAL_PIPELINE_MODEL_PARALLEL_WORLD_SIZE
         _VIRTUAL_PIPELINE_MODEL_PARALLEL_RANK = 0
@@ -143,6 +163,7 @@ def initialize_model_parallel(
 
     # Build the data-parallel groups.
     global _DATA_PARALLEL_GROUP
+    global _DATA_PARALLEL_GROUP_GLOO
     global _DATA_PARALLEL_GLOBAL_RANKS
     assert _DATA_PARALLEL_GROUP is None, 'data parallel group is already initialized'
     all_data_parallel_group_ranks = []
@@ -153,27 +174,50 @@ def initialize_model_parallel(
             ranks = range(start_rank + j, end_rank, tensor_model_parallel_size)
             all_data_parallel_group_ranks.append(list(ranks))
             group = torch.distributed.new_group(ranks)
+            group_gloo = torch.distributed.new_group(ranks, backend="gloo")
             if rank in ranks:
                 _DATA_PARALLEL_GROUP = group
+                _DATA_PARALLEL_GROUP_GLOO = group_gloo
                 _DATA_PARALLEL_GLOBAL_RANKS = ranks
 
+    # Apply SHARP to DP process groups
+    if use_sharp:
+        if rank == 0:
+            print(
+                "The number of process groups to use SHARP with depends on the type "
+                "of the network switch. Nvidia QM1 switch supports SAHRP up to 8 "
+                "process groups and QM2 supports up to 256 process groups. We apply "
+                "SHARP to the communications of the data-parallel domain. If the "
+                "number of data-parallel process groups is larger than the max "
+                "process groups that the network switch supports, the communication "
+                "will fall back to non-SHARP operators. To enable SHARP, "
+                "`#SBATCH_NETWORK=sharp` should be set in the sbatch script."
+            )
+        torch.distributed.barrier(
+            group=get_data_parallel_group(), device_ids=[torch.cuda.current_device()]
+        )
+        # Set `NCCL_SHARP_DISABLE=1` to restrict SHARP application to DP process groups
+        os.environ["NCCL_SHARP_DISABLE"] = "1"
+
     # Build the model-parallel groups.
     global _MODEL_PARALLEL_GROUP
     assert _MODEL_PARALLEL_GROUP is None, 'model parallel group is already initialized'
     for i in range(data_parallel_size):
-        ranks = [data_parallel_group_ranks[i]
-                 for data_parallel_group_ranks in all_data_parallel_group_ranks]
+        ranks = [
+            data_parallel_group_ranks[i]
+            for data_parallel_group_ranks in all_data_parallel_group_ranks
+        ]
         group = torch.distributed.new_group(ranks)
         if rank in ranks:
             _MODEL_PARALLEL_GROUP = group
 
     # Build the tensor model-parallel groups.
     global _TENSOR_MODEL_PARALLEL_GROUP
-    assert _TENSOR_MODEL_PARALLEL_GROUP is None, \
-        'tensor model parallel group is already initialized'
+    assert (
+        _TENSOR_MODEL_PARALLEL_GROUP is None
+    ), 'tensor model parallel group is already initialized'
     for i in range(num_tensor_model_parallel_groups):
-        ranks = range(i * tensor_model_parallel_size,
-                      (i + 1) * tensor_model_parallel_size)
+        ranks = range(i * tensor_model_parallel_size, (i + 1) * tensor_model_parallel_size)
         group = torch.distributed.new_group(ranks)
         if rank in ranks:
             _TENSOR_MODEL_PARALLEL_GROUP = group
@@ -182,15 +226,15 @@ def initialize_model_parallel(
     # (first and last rank in each pipeline model-parallel group).
     global _PIPELINE_MODEL_PARALLEL_GROUP
     global _PIPELINE_GLOBAL_RANKS
-    assert _PIPELINE_MODEL_PARALLEL_GROUP is None, \
-        'pipeline model parallel group is already initialized'
+    assert (
+        _PIPELINE_MODEL_PARALLEL_GROUP is None
+    ), 'pipeline model parallel group is already initialized'
     global _EMBEDDING_GROUP
     global _EMBEDDING_GLOBAL_RANKS
     assert _EMBEDDING_GROUP is None, 'embedding group is already initialized'
     global _POSITION_EMBEDDING_GROUP
     global _POSITION_EMBEDDING_GLOBAL_RANKS
-    assert _POSITION_EMBEDDING_GROUP is None, \
-        'position embedding group is already initialized'
+    assert _POSITION_EMBEDDING_GROUP is None, 'position embedding group is already initialized'
     for i in range(num_pipeline_model_parallel_groups):
         ranks = range(i, world_size, num_pipeline_model_parallel_groups)
         group = torch.distributed.new_group(ranks)
@@ -204,12 +248,13 @@ def initialize_model_parallel(
             position_embedding_ranks = [ranks[0]]
             if pipeline_model_parallel_split_rank is not None:
                 if ranks[pipeline_model_parallel_split_rank] not in embedding_ranks:
-                    embedding_ranks = [ranks[0],
-                                       ranks[pipeline_model_parallel_split_rank],
-                                       ranks[-1]]
+                    embedding_ranks = [
+                        ranks[0],
+                        ranks[pipeline_model_parallel_split_rank],
+                        ranks[-1],
+                    ]
                 if ranks[pipeline_model_parallel_split_rank] not in position_embedding_ranks:
-                    position_embedding_ranks = [ranks[0],
-                                       ranks[pipeline_model_parallel_split_rank]]
+                    position_embedding_ranks = [ranks[0], ranks[pipeline_model_parallel_split_rank]]
         else:
             embedding_ranks = ranks
             position_embedding_ranks = ranks
@@ -226,6 +271,20 @@ def initialize_model_parallel(
         if rank in ranks:
             _POSITION_EMBEDDING_GLOBAL_RANKS = position_embedding_ranks
 
+    # Build the FP8 groups.
+    global _AMAX_REDUCTION_GROUP
+    assert _AMAX_REDUCTION_GROUP is None, 'FP8 amax reduction group is already initialized'
+    if use_fp8:
+        amax_group_size: int = tensor_model_parallel_size * data_parallel_size
+        num_amax_groups: int = world_size // amax_group_size
+        for i in range(num_amax_groups):
+            start_rank = i * amax_group_size
+            end_rank = (i + 1) * amax_group_size
+            ranks = range(start_rank, end_rank)
+            group = torch.distributed.new_group(ranks)
+            if rank in ranks:
+                _AMAX_REDUCTION_GROUP = group
+
     # Initialize global memory buffer
     # This isn't really "parallel state" but there isn't another good place to
     # put this. If we end up with a more generic initialization of megatron-core
@@ -240,55 +299,68 @@ def is_unitialized():
 
 def model_parallel_is_initialized():
     """Check if model and data parallel groups are initialized."""
-    if _TENSOR_MODEL_PARALLEL_GROUP is None or \
-        _PIPELINE_MODEL_PARALLEL_GROUP is None or \
-        _DATA_PARALLEL_GROUP is None:
+    if (
+        _TENSOR_MODEL_PARALLEL_GROUP is None
+        or _PIPELINE_MODEL_PARALLEL_GROUP is None
+        or _DATA_PARALLEL_GROUP is None
+    ):
         return False
     return True
 
 
 def get_model_parallel_group():
     """Get the model parallel group the caller rank belongs to."""
-    assert _MODEL_PARALLEL_GROUP is not None, \
-        'model parallel group is not initialized'
+    assert _MODEL_PARALLEL_GROUP is not None, 'model parallel group is not initialized'
     return _MODEL_PARALLEL_GROUP
 
 
-def get_tensor_model_parallel_group():
+def get_tensor_model_parallel_group(check_initialized=True):
     """Get the tensor model parallel group the caller rank belongs to."""
-    assert _TENSOR_MODEL_PARALLEL_GROUP is not None, \
-        'intra_layer_model parallel group is not initialized'
+    if check_initialized:
+        assert (
+            _TENSOR_MODEL_PARALLEL_GROUP is not None
+        ), 'tensor model parallel group is not initialized'
     return _TENSOR_MODEL_PARALLEL_GROUP
 
 
 def get_pipeline_model_parallel_group():
     """Get the pipeline model parallel group the caller rank belongs to."""
-    assert _PIPELINE_MODEL_PARALLEL_GROUP is not None, \
-        'pipeline_model parallel group is not initialized'
+    assert (
+        _PIPELINE_MODEL_PARALLEL_GROUP is not None
+    ), 'pipeline_model parallel group is not initialized'
     return _PIPELINE_MODEL_PARALLEL_GROUP
 
 
 def get_data_parallel_group():
     """Get the data parallel group the caller rank belongs to."""
-    assert _DATA_PARALLEL_GROUP is not None, \
-        'data parallel group is not initialized'
+    assert _DATA_PARALLEL_GROUP is not None, 'data parallel group is not initialized'
     return _DATA_PARALLEL_GROUP
 
 
+def get_data_parallel_group_gloo():
+    """Get the data parallel group-gloo the caller rank belongs to."""
+    assert _DATA_PARALLEL_GROUP_GLOO is not None, 'data parallel group-gloo is not initialized'
+    return _DATA_PARALLEL_GROUP_GLOO
+
+
 def get_embedding_group():
     """Get the embedding group the caller rank belongs to."""
-    assert _EMBEDDING_GROUP is not None, \
-        'embedding group is not initialized'
+    assert _EMBEDDING_GROUP is not None, 'embedding group is not initialized'
     return _EMBEDDING_GROUP
 
 
 def get_position_embedding_group():
     """Get the position embedding group the caller rank belongs to."""
-    assert _POSITION_EMBEDDING_GROUP is not None, \
-        'position embedding group is not initialized'
+    assert _POSITION_EMBEDDING_GROUP is not None, 'position embedding group is not initialized'
     return _POSITION_EMBEDDING_GROUP
 
 
+def get_amax_reduction_group():
+    """Get the FP8 amax reduction group the caller rank belongs to."""
+    assert _AMAX_REDUCTION_GROUP is not None, 'FP8 amax reduction group is not initialized'
+    return _AMAX_REDUCTION_GROUP
+
+
 def set_tensor_model_parallel_world_size(world_size):
     """Set the tensor model parallel size"""
     global _MPU_TENSOR_MODEL_PARALLEL_WORLD_SIZE
@@ -301,6 +373,12 @@ def set_pipeline_model_parallel_world_size(world_size):
     _MPU_PIPELINE_MODEL_PARALLEL_WORLD_SIZE = world_size
 
 
+def set_virtual_pipeline_model_parallel_world_size(world_size):
+    """Set the pipeline model parallel size"""
+    global _VIRTUAL_PIPELINE_MODEL_PARALLEL_WORLD_SIZE
+    _VIRTUAL_PIPELINE_MODEL_PARALLEL_WORLD_SIZE = world_size
+
+
 def get_tensor_model_parallel_world_size():
     """Return world size for the tensor model parallel group."""
     global _MPU_TENSOR_MODEL_PARALLEL_WORLD_SIZE
@@ -360,8 +438,10 @@ def get_pipeline_model_parallel_split_rank():
 def is_pipeline_first_stage(ignore_virtual=False):
     """Return True if in the first pipeline model-parallel stage, False otherwise."""
     if not ignore_virtual:
-        if get_virtual_pipeline_model_parallel_world_size() is not None and \
-            get_virtual_pipeline_model_parallel_rank() != 0:
+        if (
+            get_virtual_pipeline_model_parallel_world_size() is not None
+            and get_virtual_pipeline_model_parallel_rank() != 0
+        ):
             return False
     return get_pipeline_model_parallel_rank() == 0
 
@@ -369,14 +449,14 @@ def is_pipeline_first_stage(ignore_virtual=False):
 def is_pipeline_last_stage(ignore_virtual=False):
     """Return True if in the last pipeline model-parallel stage, False otherwise."""
     if not ignore_virtual:
-        virtual_pipeline_model_parallel_world_size = \
+        virtual_pipeline_model_parallel_world_size = (
             get_virtual_pipeline_model_parallel_world_size()
-        if virtual_pipeline_model_parallel_world_size is not None and \
-            get_virtual_pipeline_model_parallel_rank() != (
-                virtual_pipeline_model_parallel_world_size - 1):
+        )
+        if virtual_pipeline_model_parallel_world_size is not None and get_virtual_pipeline_model_parallel_rank() != (
+            virtual_pipeline_model_parallel_world_size - 1
+        ):
             return False
-    return get_pipeline_model_parallel_rank() == (
-        get_pipeline_model_parallel_world_size() - 1)
+    return get_pipeline_model_parallel_rank() == (get_pipeline_model_parallel_world_size() - 1)
 
 
 def is_rank_in_embedding_group(ignore_virtual=False):
@@ -437,8 +517,7 @@ def is_pipeline_stage_at_split():
     stage executes encoder block for a model with both encoder and
     decoder."""
     rank = get_pipeline_model_parallel_rank()
-    return is_pipeline_stage_before_split(rank) and \
-            is_pipeline_stage_after_split(rank+1)
+    return is_pipeline_stage_before_split(rank) and is_pipeline_stage_after_split(rank + 1)
 
 
 def get_virtual_pipeline_model_parallel_rank():
@@ -459,12 +538,6 @@ def get_virtual_pipeline_model_parallel_world_size():
     return _VIRTUAL_PIPELINE_MODEL_PARALLEL_WORLD_SIZE
 
 
-def set_virtual_pipeline_model_parallel_world_size(world_size):
-    """Set the virtual pipeline-parallel world size"""
-    global _VIRTUAL_PIPELINE_MODEL_PARALLEL_WORLD_SIZE
-    _VIRTUAL_PIPELINE_MODEL_PARALLEL_WORLD_SIZE = world_size
-
-
 def get_tensor_model_parallel_src_rank():
     """Calculate the global rank corresponding to the first local rank
     in the tensor model parallel group."""
@@ -476,31 +549,28 @@ def get_tensor_model_parallel_src_rank():
 def get_data_parallel_src_rank():
     """Calculate the global rank corresponding to the first local rank
     in the data parallel group."""
-    assert _DATA_PARALLEL_GLOBAL_RANKS is not None, \
-        "Data parallel group is not initialized"
+    assert _DATA_PARALLEL_GLOBAL_RANKS is not None, "Data parallel group is not initialized"
     return _DATA_PARALLEL_GLOBAL_RANKS[0]
 
 
 def get_pipeline_model_parallel_first_rank():
     """Return the global rank of the first process in the pipeline for the
     current tensor parallel group"""
-    assert _PIPELINE_GLOBAL_RANKS is not None, \
-        "Pipeline parallel group is not initialized"
+    assert _PIPELINE_GLOBAL_RANKS is not None, "Pipeline parallel group is not initialized"
     return _PIPELINE_GLOBAL_RANKS[0]
 
 
 def get_pipeline_model_parallel_last_rank():
     """Return the global rank of the last process in the pipeline for the
     current tensor parallel group"""
-    assert _PIPELINE_GLOBAL_RANKS is not None, \
-        "Pipeline parallel group is not initialized"
+    assert _PIPELINE_GLOBAL_RANKS is not None, "Pipeline parallel group is not initialized"
     last_rank_local = get_pipeline_model_parallel_world_size() - 1
     return _PIPELINE_GLOBAL_RANKS[last_rank_local]
 
+
 def get_pipeline_model_parallel_next_rank():
     """Return the global rank that follows the caller in the pipeline"""
-    assert _PIPELINE_GLOBAL_RANKS is not None, \
-        "Pipeline parallel group is not initialized"
+    assert _PIPELINE_GLOBAL_RANKS is not None, "Pipeline parallel group is not initialized"
     rank_in_pipeline = get_pipeline_model_parallel_rank()
     world_size = get_pipeline_model_parallel_world_size()
     return _PIPELINE_GLOBAL_RANKS[(rank_in_pipeline + 1) % world_size]
@@ -508,8 +578,7 @@ def get_pipeline_model_parallel_next_rank():
 
 def get_pipeline_model_parallel_prev_rank():
     """Return the global rank that preceeds the caller in the pipeline"""
-    assert _PIPELINE_GLOBAL_RANKS is not None, \
-        "Pipeline parallel group is not initialized"
+    assert _PIPELINE_GLOBAL_RANKS is not None, "Pipeline parallel group is not initialized"
     rank_in_pipeline = get_pipeline_model_parallel_rank()
     world_size = get_pipeline_model_parallel_world_size()
     return _PIPELINE_GLOBAL_RANKS[(rank_in_pipeline - 1) % world_size]
@@ -517,12 +586,19 @@ def get_pipeline_model_parallel_prev_rank():
 
 def get_data_parallel_world_size():
     """Return world size for the data parallel group."""
-    return torch.distributed.get_world_size(group=get_data_parallel_group())
+    if torch.distributed.is_available() and torch.distributed.is_initialized():
+        return torch.distributed.get_world_size(group=get_data_parallel_group())
+    else:
+        return 0
 
 
 def get_data_parallel_rank():
     """Return my rank for the data parallel group."""
-    return torch.distributed.get_rank(group=get_data_parallel_group())
+    if torch.distributed.is_available() and torch.distributed.is_initialized():
+        return torch.distributed.get_rank(group=get_data_parallel_group())
+    else:
+        return 0
+
 
 def _set_global_memory_buffer():
     """Initialize global buffer"""
@@ -530,12 +606,19 @@ def _set_global_memory_buffer():
     assert _GLOBAL_MEMORY_BUFFER is None, 'global memory buffer is already initialized'
     _GLOBAL_MEMORY_BUFFER = GlobalMemoryBuffer()
 
+
 def get_global_memory_buffer():
     """Return the global GlobalMemoryBuffer object"""
     assert _GLOBAL_MEMORY_BUFFER is not None, 'global memory buffer is not initialized'
     return _GLOBAL_MEMORY_BUFFER
 
 
+def destroy_global_memory_buffer():
+    """Sets the global memory buffer to None"""
+    global _GLOBAL_MEMORY_BUFFER
+    _GLOBAL_MEMORY_BUFFER = None
+
+
 def destroy_model_parallel():
     """Set the groups to none."""
     global _MODEL_PARALLEL_GROUP
@@ -550,6 +633,8 @@ def destroy_model_parallel():
     _EMBEDDING_GROUP = None
     global _POSITION_EMBEDDING_GROUP
     _POSITION_EMBEDDING_GROUP = None
+    global _AMAX_REDUCTION_GROUP
+    _AMAX_REDUCTION_GROUP = None
     global _VIRTUAL_PIPELINE_MODEL_PARALLEL_RANK
     _VIRTUAL_PIPELINE_MODEL_PARALLEL_RANK = None
     global _VIRTUAL_PIPELINE_MODEL_PARALLEL_WORLD_SIZE

megatron/core/pipeline_parallel/p2p_communication.py

 # Copyright (c) 2022, NVIDIA CORPORATION. All rights reserved.
 
-from functools import reduce
 import operator
-from typing import Optional, List, Union, Callable, Tuple
+from functools import reduce
+from typing import Callable, List, Optional, Tuple, Union
 
 import torch
 
 from megatron import core
+from megatron.core import ModelParallelConfig
 from megatron.core.parallel_state import (
     get_pipeline_model_parallel_group,
-    get_pipeline_model_parallel_prev_rank,
     get_pipeline_model_parallel_next_rank,
+    get_pipeline_model_parallel_prev_rank,
+    get_pipeline_model_parallel_rank,
 )
 
 # Types
 Shape = Union[List[int], torch.Size]
 
-def _communicate_shapes(tensor_send_next, tensor_send_prev,
-                        recv_prev, recv_next,
-                        use_ring_exchange_p2p):
+
+def _communicate_shapes(tensor_send_next, tensor_send_prev, recv_prev, recv_next, config):
     """Communicate tensor shapes between stages. Used to communicate
     tensor shapes before the actual tensor communication happens.
     This is required when the sequence lengths across micro batches
@@ -42,49 +43,59 @@ def _communicate_shapes(tensor_send_next, tensor_send_prev,
     send_prev_shape_tensor = None
     send_next_shape_tensor = None
     if recv_prev:
-        recv_prev_shape_tensor = torch.empty((3),
-                                             device=torch.cuda.current_device(),
-                                             dtype=torch.int64)
+        recv_prev_shape_tensor = torch.empty(
+            (3), device=torch.cuda.current_device(), dtype=torch.int64
+        )
     if recv_next:
-        recv_next_shape_tensor = torch.empty((3),
-                                             device=torch.cuda.current_device(),
-                                             dtype=torch.int64)
+        recv_next_shape_tensor = torch.empty(
+            (3), device=torch.cuda.current_device(), dtype=torch.int64
+        )
     if tensor_send_prev is not None:
-        send_prev_shape_tensor = torch.tensor(tensor_send_prev.size(),
-                                              device=torch.cuda.current_device(),
-                                              dtype=torch.int64)
+        send_prev_shape_tensor = torch.tensor(
+            tensor_send_prev.size(), device=torch.cuda.current_device(), dtype=torch.int64
+        )
     if tensor_send_next is not None:
-        send_next_shape_tensor = torch.tensor(tensor_send_next.size(),
-                                              device=torch.cuda.current_device(),
-                                              dtype=torch.int64)
-
-    if use_ring_exchange_p2p:
-        torch.distributed.ring_exchange(tensor_send_prev=send_prev_shape_tensor,
-                                        tensor_recv_prev=recv_prev_shape_tensor,
-                                        tensor_send_next=send_next_shape_tensor,
-                                        tensor_recv_next=recv_next_shape_tensor,
-                                        group=mpu.get_pipeline_model_parallel_group())
+        send_next_shape_tensor = torch.tensor(
+            tensor_send_next.size(), device=torch.cuda.current_device(), dtype=torch.int64
+        )
+
+    if config.use_ring_exchange_p2p:
+        torch.distributed.ring_exchange(
+            tensor_send_prev=send_prev_shape_tensor,
+            tensor_recv_prev=recv_prev_shape_tensor,
+            tensor_send_next=send_next_shape_tensor,
+            tensor_recv_next=recv_next_shape_tensor,
+            group=get_pipeline_model_parallel_group(),
+        )
     else:
         ops = []
         if send_prev_shape_tensor is not None:
             send_prev_op = torch.distributed.P2POp(
-                torch.distributed.isend, send_prev_shape_tensor,
-                mpu.get_pipeline_model_parallel_prev_rank())
+                torch.distributed.isend,
+                send_prev_shape_tensor,
+                get_pipeline_model_parallel_prev_rank(),
+            )
             ops.append(send_prev_op)
         if recv_prev_shape_tensor is not None:
             recv_prev_op = torch.distributed.P2POp(
-                torch.distributed.irecv, recv_prev_shape_tensor,
-                mpu.get_pipeline_model_parallel_prev_rank())
+                torch.distributed.irecv,
+                recv_prev_shape_tensor,
+                get_pipeline_model_parallel_prev_rank(),
+            )
             ops.append(recv_prev_op)
         if send_next_shape_tensor is not None:
             send_next_op = torch.distributed.P2POp(
-                torch.distributed.isend, send_next_shape_tensor,
-                mpu.get_pipeline_model_parallel_next_rank())
+                torch.distributed.isend,
+                send_next_shape_tensor,
+                get_pipeline_model_parallel_next_rank(),
+            )
             ops.append(send_next_op)
         if recv_next_shape_tensor is not None:
             recv_next_op = torch.distributed.P2POp(
-                torch.distributed.irecv, recv_next_shape_tensor,
-                mpu.get_pipeline_model_parallel_next_rank())
+                torch.distributed.irecv,
+                recv_next_shape_tensor,
+                get_pipeline_model_parallel_next_rank(),
+            )
             ops.append(recv_next_op)
         if len(ops) > 0:
             reqs = torch.distributed.batch_isend_irecv(ops)
@@ -106,15 +117,126 @@ def _communicate_shapes(tensor_send_next, tensor_send_prev,
     return recv_prev_shape, recv_next_shape
 
 
-def _communicate(*, tensor_send_next: Optional[torch.Tensor],
-                 tensor_send_prev: Optional[torch.Tensor],
-                 recv_prev: bool,
-                 recv_next: bool,
-                 tensor_shape: Shape,
-                 dtype: Optional[torch.dtype],
-                 variable_seq_lengths: bool = False,
-                 use_ring_exchange_p2p: bool = False,
-                 ) -> Tuple[torch.Tensor, torch.Tensor]:
+def _batched_p2p_ops(
+    *,
+    tensor_send_prev: Optional[torch.Tensor],
+    tensor_recv_prev: Optional[torch.Tensor],
+    tensor_send_next: Optional[torch.Tensor],
+    tensor_recv_next: Optional[torch.Tensor],
+    group: torch.distributed.ProcessGroup
+):
+    ops = []
+    if tensor_send_prev is not None:
+        send_prev_op = torch.distributed.P2POp(
+            torch.distributed.isend,
+            tensor_send_prev,
+            get_pipeline_model_parallel_prev_rank(),
+            group,
+        )
+        ops.append(send_prev_op)
+    if tensor_recv_prev is not None:
+        recv_prev_op = torch.distributed.P2POp(
+            torch.distributed.irecv,
+            tensor_recv_prev,
+            get_pipeline_model_parallel_prev_rank(),
+            group,
+        )
+        ops.append(recv_prev_op)
+    if tensor_send_next is not None:
+        send_next_op = torch.distributed.P2POp(
+            torch.distributed.isend,
+            tensor_send_next,
+            get_pipeline_model_parallel_next_rank(),
+            group,
+        )
+        ops.append(send_next_op)
+    if tensor_recv_next is not None:
+        recv_next_op = torch.distributed.P2POp(
+            torch.distributed.irecv,
+            tensor_recv_next,
+            get_pipeline_model_parallel_next_rank(),
+            group,
+        )
+        ops.append(recv_next_op)
+    if len(ops) > 0:
+        reqs = torch.distributed.batch_isend_irecv(ops)
+    else:
+        reqs = []
+    return reqs
+
+
+def _p2p_ops(
+    *,
+    tensor_send_prev: Optional[torch.Tensor],
+    tensor_recv_prev: Optional[torch.Tensor],
+    tensor_send_next: Optional[torch.Tensor],
+    tensor_recv_next: Optional[torch.Tensor],
+    group: torch.distributed.ProcessGroup
+):
+    reqs = []
+    rank = get_pipeline_model_parallel_rank()
+    if get_pipeline_model_parallel_rank() % 2 == 0:
+        if tensor_send_next is not None:
+            send_next_req = torch.distributed.isend(
+                tensor=tensor_send_next, dst=get_pipeline_model_parallel_next_rank(), group=group,
+            )
+            reqs.append(send_next_req)
+
+        if tensor_recv_prev is not None:
+            recv_prev_req = torch.distributed.irecv(
+                tensor=tensor_recv_prev, src=get_pipeline_model_parallel_prev_rank(), group=group,
+            )
+            reqs.append(recv_prev_req)
+
+        if tensor_send_prev is not None:
+            send_prev_req = torch.distributed.isend(
+                tensor=tensor_send_prev, dst=get_pipeline_model_parallel_prev_rank(), group=group,
+            )
+            reqs.append(send_prev_req)
+
+        if tensor_recv_next is not None:
+            recv_next_req = torch.distributed.irecv(
+                tensor=tensor_recv_next, src=get_pipeline_model_parallel_next_rank(), group=group,
+            )
+            reqs.append(recv_next_req)
+
+    else:
+        if tensor_recv_prev is not None:
+            recv_prev_req = torch.distributed.irecv(
+                tensor=tensor_recv_prev, src=get_pipeline_model_parallel_prev_rank(), group=group,
+            )
+            reqs.append(recv_prev_req)
+
+        if tensor_send_next is not None:
+            send_next_req = torch.distributed.isend(
+                tensor=tensor_send_next, dst=get_pipeline_model_parallel_next_rank(), group=group,
+            )
+            reqs.append(send_next_req)
+
+        if tensor_recv_next is not None:
+            recv_next_req = torch.distributed.irecv(
+                tensor=tensor_recv_next, src=get_pipeline_model_parallel_next_rank(), group=group,
+            )
+            reqs.append(recv_next_req)
+
+        if tensor_send_prev is not None:
+            send_prev_req = torch.distributed.isend(
+                tensor=tensor_send_prev, dst=get_pipeline_model_parallel_prev_rank(), group=group,
+            )
+            reqs.append(send_prev_req)
+    return reqs
+
+
+def _communicate(
+    *,
+    tensor_send_next: Optional[torch.Tensor],
+    tensor_send_prev: Optional[torch.Tensor],
+    recv_prev: bool,
+    recv_next: bool,
+    tensor_shape: Shape,
+    config: ModelParallelConfig,
+    wait_on_reqs: bool = True
+) -> Tuple[torch.Tensor, torch.Tensor]:
     """Communicate tensors between stages. Used as helper method in other
     communication methods that are used in megatron/schedules.py.
 
@@ -136,23 +258,9 @@ def _communicate(*, tensor_send_next: Optional[torch.Tensor],
             tensors sent and received in a single function call are
             the same shape).
 
-        dtype (torch.dtype, required if either recv_{prev,next} is True):
-            this must be the type of the tensors that will be
-            received, will typically be params_dtype, but in the case
-            of fp32 residual connections might be torch.float.
-
-        variable_seq_lengths (bool, optional, default=False):
-            Support for variable sequence lengths across
-            microbatches. Setting this communicates the size of
-            tensors during pipeline parallelism communication, because
-            of this extra overhead it should only be set if the
-            sequence length is not constant during training.
-
-        use_ring_exchange_p2p (bool, optional, default = False):
-            Use custom ring_exchange kernel instead of
-            torch.distributed.batch_isend_irecv(). Requires custom
-            built torch with torch.distributed.ring_exchange.
-
+        wait_on_reqs (boolean, optional, default=False):
+            For non-batched p2p communication, wait on each request
+            before returning.
 
     Returns:
         tuple containing
@@ -167,84 +275,79 @@ def _communicate(*, tensor_send_next: Optional[torch.Tensor],
     tensor_recv_prev = None
     tensor_recv_next = None
 
-    if not variable_seq_lengths:
+    if not config.variable_seq_lengths:
         recv_prev_shape = tensor_shape
         recv_next_shape = tensor_shape
     else:
-        recv_prev_shape, recv_next_shape = \
-            _communicate_shapes(tensor_send_next,
-                                tensor_send_prev,
-                                recv_prev,
-                                recv_next)
+        recv_prev_shape, recv_next_shape = _communicate_shapes(
+            tensor_send_next, tensor_send_prev, recv_prev, recv_next, config
+        )
 
     if recv_prev:
-        if dtype is None:
-            raise RuntimeError("dtype must be provided if recv_prev is True")
+        if config.pipeline_dtype is None:
+            raise RuntimeError("pipeline_dtype must be provided if recv_prev is True")
         if tensor_shape is None:
             raise RuntimeError(
                 "tensor_shape must be specified if recv_prev is True. "
                 "Common tensor_shape is (seq_length, micro_batch_size, hidden_size)"
             )
-        tensor_recv_prev = torch.empty(recv_prev_shape,
-                                       requires_grad=True,
-                                       device=torch.cuda.current_device(),
-                                       dtype=dtype)
+        tensor_recv_prev = torch.empty(
+            recv_prev_shape,
+            requires_grad=True,
+            device=torch.cuda.current_device(),
+            dtype=config.pipeline_dtype,
+        )
     if recv_next:
-        if dtype is None:
+        if config.pipeline_dtype is None:
             raise RuntimeError("dtype must be provided if recv_next is True")
         if tensor_shape is None:
             raise RuntimeError(
                 "tensor_shape must be specified if recv_next is True. "
                 "Common tensor_shape is (seq_length, micro_batch_size, hidden_size)"
             )
-        tensor_recv_next = torch.empty(recv_next_shape,
-                                       requires_grad=True,
-                                       device=torch.cuda.current_device(),
-                                       dtype=dtype)
+        tensor_recv_next = torch.empty(
+            recv_next_shape,
+            requires_grad=True,
+            device=torch.cuda.current_device(),
+            dtype=config.pipeline_dtype,
+        )
 
     # Send tensors in both the forward and backward directions as appropriate.
-    if use_ring_exchange_p2p:
-        torch.distributed.ring_exchange(tensor_send_prev=tensor_send_prev,
-                                        tensor_recv_prev=tensor_recv_prev,
-                                        tensor_send_next=tensor_send_next,
-                                        tensor_recv_next=tensor_recv_next,
-                                        group=get_pipeline_model_parallel_group())
+    if config.use_ring_exchange_p2p:
+
+        def _ring_exchange_wrapper(**kwargs):
+            torch.distributed.ring_exchange(**kwargs)
+            return []
+
+        p2p_func = _ring_exchange_wrapper
+    elif config.batch_p2p_comm:
+        assert wait_on_reqs
+        p2p_func = _batched_p2p_ops
     else:
-        ops = []
-        if tensor_send_prev is not None:
-            send_prev_op = torch.distributed.P2POp(
-                torch.distributed.isend, tensor_send_prev,
-                get_pipeline_model_parallel_prev_rank())
-            ops.append(send_prev_op)
-        if tensor_recv_prev is not None:
-            recv_prev_op = torch.distributed.P2POp(
-                torch.distributed.irecv, tensor_recv_prev,
-                get_pipeline_model_parallel_prev_rank())
-            ops.append(recv_prev_op)
-        if tensor_send_next is not None:
-            send_next_op = torch.distributed.P2POp(
-                torch.distributed.isend, tensor_send_next,
-                get_pipeline_model_parallel_next_rank())
-            ops.append(send_next_op)
-        if tensor_recv_next is not None:
-            recv_next_op = torch.distributed.P2POp(
-                torch.distributed.irecv, tensor_recv_next,
-                get_pipeline_model_parallel_next_rank())
-            ops.append(recv_next_op)
-        if len(ops) > 0:
-            reqs = torch.distributed.batch_isend_irecv(ops)
-            for req in reqs:
-                req.wait()
+        p2p_func = _p2p_ops
+
+    reqs = p2p_func(
+        tensor_send_prev=tensor_send_prev,
+        tensor_recv_prev=tensor_recv_prev,
+        tensor_send_next=tensor_send_next,
+        tensor_recv_next=tensor_recv_next,
+        group=get_pipeline_model_parallel_group(),
+    )
+
+    if wait_on_reqs and len(reqs) > 0:
+        for req in reqs:
+            req.wait()
+        reqs = None
+
+    if config.batch_p2p_comm and config.batch_p2p_sync:
         # To protect against race condition when using batch_isend_irecv().
         # User should assert that we have a modern enough PyTorch to not need this
         torch.cuda.synchronize()
 
-    return tensor_recv_prev, tensor_recv_next
+    return tensor_recv_prev, tensor_recv_next, reqs
 
 
-def recv_forward(tensor_shape: Shape,
-                 dtype: torch.dtype,
-                 timers: Callable = None) -> torch.Tensor:
+def recv_forward(tensor_shape: Shape, config: ModelParallelConfig) -> torch.Tensor:
     """ Receive tensor from previous rank in pipeline (forward receive).
 
 
@@ -254,23 +357,22 @@ def recv_forward(tensor_shape: Shape,
     if core.parallel_state.is_pipeline_first_stage():
         input_tensor = None
     else:
-        if timers is not None:
-            timers('forward-recv', log_level=2).start()
-        input_tensor, _ = _communicate(
+        if config.timers is not None:
+            config.timers('forward-recv', log_level=2).start()
+        input_tensor, _, _ = _communicate(
             tensor_send_next=None,
             tensor_send_prev=None,
             recv_prev=True,
             recv_next=False,
             tensor_shape=tensor_shape,
-            dtype=dtype)
-        if timers is not None:
-            timers('forward-recv').stop()
+            config=config,
+        )
+        if config.timers is not None:
+            config.timers('forward-recv').stop()
     return input_tensor
 
 
-def recv_backward(tensor_shape: Shape,
-                  dtype: torch.dtype,
-                  timers: Callable = None) -> torch.Tensor:
+def recv_backward(tensor_shape: Shape, config: ModelParallelConfig) -> torch.Tensor:
     """Receive tensor from next rank in pipeline (backward receive).
 
     See _communicate for argument details.
@@ -278,65 +380,65 @@ def recv_backward(tensor_shape: Shape,
     if core.parallel_state.is_pipeline_last_stage():
         output_tensor_grad = None
     else:
-        if timers is not None:
-            timers('backward-recv', log_level=2).start()
-        _, output_tensor_grad = _communicate(
+        if config.timers is not None:
+            config.timers('backward-recv', log_level=2).start()
+        _, output_tensor_grad, _ = _communicate(
             tensor_send_next=None,
             tensor_send_prev=None,
             recv_prev=False,
             recv_next=True,
             tensor_shape=tensor_shape,
-            dtype=dtype)
-        if timers is not None:
-            timers('backward-recv').stop()
+            config=config,
+        )
+        if config.timers is not None:
+            config.timers('backward-recv').stop()
     return output_tensor_grad
 
 
-def send_forward(output_tensor: torch.Tensor,
-                 timers: Callable = None) -> None:
+def send_forward(output_tensor: torch.Tensor, config: ModelParallelConfig) -> None:
     """Send tensor to next rank in pipeline (forward send).
 
     See _communicate for argument details.
     """
 
     if not core.parallel_state.is_pipeline_last_stage():
-        if timers is not None:
-            timers('forward-send', log_level=2).start()
+        if config.timers is not None:
+            config.timers('forward-send', log_level=2).start()
         _communicate(
             tensor_send_next=output_tensor,
             tensor_send_prev=None,
             recv_prev=False,
             recv_next=False,
             tensor_shape=None,
-            dtype=None)
-        if timers is not None:
-            timers('forward-send').stop()
+            config=config,
+        )
+        if config.timers is not None:
+            config.timers('forward-send').stop()
 
 
-def send_backward(input_tensor_grad: torch.Tensor,
-                  timers: Callable = None) -> None:
+def send_backward(input_tensor_grad: torch.Tensor, config: ModelParallelConfig) -> None:
     """Send tensor to previous rank in pipeline (backward send).
 
     See _communicate for argument details.
     """
     if not core.parallel_state.is_pipeline_first_stage():
-        if timers is not None:
-            timers('backward-send', log_level=2).start()
+        if config.timers is not None:
+            config.timers('backward-send', log_level=2).start()
         _communicate(
             tensor_send_next=None,
             tensor_send_prev=input_tensor_grad,
             recv_prev=False,
             recv_next=False,
             tensor_shape=None,
-            dtype=None)
-        if timers is not None:
-            timers('backward-send').stop()
+            config=config,
+        )
+        if config.timers is not None:
+            config.timers('backward-send').stop()
 
 
-def send_forward_recv_backward(output_tensor: torch.Tensor,
-                               tensor_shape: Shape,
-                               dtype: torch.dtype,
-                               timers: Callable = None) -> torch.Tensor:
+def send_forward_recv_backward(
+    output_tensor: torch.Tensor, tensor_shape: Shape, config: ModelParallelConfig
+) -> torch.Tensor:
     """Batched send and recv with next rank in pipeline.
 
     See _communicate for argument details.
@@ -344,24 +446,24 @@ def send_forward_recv_backward(output_tensor: torch.Tensor,
     if core.parallel_state.is_pipeline_last_stage():
         output_tensor_grad = None
     else:
-        if timers is not None:
-            timers('forward-send-backward-recv', log_level=2).start()
-        _, output_tensor_grad = _communicate(
+        if config.timers is not None:
+            config.timers('forward-send-backward-recv', log_level=2).start()
+        _, output_tensor_grad, _ = _communicate(
             tensor_send_next=output_tensor,
             tensor_send_prev=None,
             recv_prev=False,
             recv_next=True,
             tensor_shape=tensor_shape,
-            dtype=dtype)
-        if timers is not None:
-            timers('forward-send-backward-recv').stop()
+            config=config,
+        )
+        if config.timers is not None:
+            config.timers('forward-send-backward-recv').stop()
     return output_tensor_grad
 
 
-def send_backward_recv_forward(input_tensor_grad: torch.Tensor,
-                               tensor_shape: Shape,
-                               dtype: torch.dtype,
-                               timers: Callable = None) -> torch.Tensor:
+def send_backward_recv_forward(
+    input_tensor_grad: torch.Tensor, tensor_shape: Shape, config: ModelParallelConfig
+) -> torch.Tensor:
     """Batched send and recv with previous rank in pipeline.
 
     See _communicate for argument details.
@@ -369,88 +471,101 @@ def send_backward_recv_forward(input_tensor_grad: torch.Tensor,
     if core.parallel_state.is_pipeline_first_stage():
         input_tensor = None
     else:
-        if timers is not None:
-            timers('backward-send-forward-recv', log_level=2).start()
-        input_tensor, _ = _communicate(
+        if config.timers is not None:
+            config.timers('backward-send-forward-recv', log_level=2).start()
+        input_tensor, _, _ = _communicate(
             tensor_send_next=None,
             tensor_send_prev=input_tensor_grad,
             recv_prev=True,
             recv_next=False,
             tensor_shape=tensor_shape,
-            dtype=dtype)
-        if timers is not None:
-            timers('backward-send-forward-recv').stop()
+            config=config,
+        )
+        if config.timers is not None:
+            config.timers('backward-send-forward-recv').stop()
     return input_tensor
 
 
-def send_forward_recv_forward(output_tensor: torch.Tensor,
-                              recv_prev: bool,
-                              tensor_shape: Shape,
-                              dtype: torch.dtype,
-                              timers: Callable = None) -> torch.Tensor:
+def send_forward_recv_forward(
+    output_tensor: torch.Tensor,
+    recv_prev: bool,
+    tensor_shape: Shape,
+    config: ModelParallelConfig,
+    overlap_p2p_comm: bool = False,
+) -> torch.Tensor:
     """Batched recv from previous rank and send to next rank in pipeline.
 
     See _communicate for argument details.
     """
-    if timers is not None:
-        timers('forward-send-forward-recv', log_level=2).start()
-    input_tensor, _ = _communicate(
+    if config.timers is not None:
+        config.timers('forward-send-forward-recv', log_level=2).start()
+    input_tensor, _, wait_handles = _communicate(
         tensor_send_next=output_tensor,
         tensor_send_prev=None,
         recv_prev=recv_prev,
         recv_next=False,
         tensor_shape=tensor_shape,
-        dtype=dtype)
-    if timers is not None:
-        timers('forward-send-forward-recv').stop()
+        wait_on_reqs=(not overlap_p2p_comm),
+        config=config,
+    )
+    if config.timers is not None:
+        config.timers('forward-send-forward-recv').stop()
+    if overlap_p2p_comm:
+        return input_tensor, wait_handles
     return input_tensor
 
 
-def send_backward_recv_backward(input_tensor_grad: torch.Tensor,
-                                recv_next: bool,
-                                tensor_shape: Shape,
-                                dtype: torch.dtype,
-                                timers: Callable = None) -> torch.Tensor:
+def send_backward_recv_backward(
+    input_tensor_grad: torch.Tensor,
+    recv_next: bool,
+    tensor_shape: Shape,
+    config: ModelParallelConfig,
+    overlap_p2p_comm: bool = False,
+) -> torch.Tensor:
     """Batched recv from next rank and send to previous rank in pipeline.
 
     See _communicate for argument details.
     """
-    if timers is not None:
-        timers('backward-send-backward-recv', log_level=2).start()
-    _, output_tensor_grad = _communicate(
+    if config.timers is not None:
+        config.timers('backward-send-backward-recv', log_level=2).start()
+    _, output_tensor_grad, wait_handles = _communicate(
         tensor_send_next=None,
         tensor_send_prev=input_tensor_grad,
         recv_prev=False,
         recv_next=recv_next,
         tensor_shape=tensor_shape,
-        dtype=dtype)
-    if timers is not None:
-        timers('backward-send-backward-recv').stop()
+        wait_on_reqs=(not overlap_p2p_comm),
+        config=config,
+    )
+    if config.timers is not None:
+        config.timers('backward-send-backward-recv').stop()
+    if overlap_p2p_comm:
+        return output_tensor_grad, wait_handles
     return output_tensor_grad
 
 
 def send_forward_backward_recv_forward_backward(
-        output_tensor: torch.Tensor,
-        input_tensor_grad: torch.Tensor,
-        recv_prev: bool,
-        recv_next: bool,
-        tensor_shape: Shape,
-        dtype: torch.dtype,
-        timers: Callable = None) -> Tuple[torch.Tensor, torch.Tensor]:
+    output_tensor: torch.Tensor,
+    input_tensor_grad: torch.Tensor,
+    recv_prev: bool,
+    recv_next: bool,
+    tensor_shape: Shape,
+    config: ModelParallelConfig,
+) -> torch.Tensor:
     """Batched send and recv with previous and next ranks in pipeline.
 
     See _communicate for argument details.
     """
-    if timers is not None:
-        timers('forward-backward-send-forward-backward-recv',
-               log_level=2).start()
-    input_tensor, output_tensor_grad = _communicate(
+    if config.timers is not None:
+        config.timers('forward-backward-send-forward-backward-recv', log_level=2).start()
+    input_tensor, output_tensor_grad, _ = _communicate(
         tensor_send_next=output_tensor,
         tensor_send_prev=input_tensor_grad,
         recv_prev=recv_prev,
         recv_next=recv_next,
         tensor_shape=tensor_shape,
-        dtype=dtype)
-    if timers is not None:
-        timers('forward-backward-send-forward-backward-recv').stop()
+        config=config,
+    )
+    if config.timers is not None:
+        config.timers('forward-backward-send-forward-backward-recv').stop()
     return input_tensor, output_tensor_grad

megatron/core/pipeline_parallel/schedules.py

 # Copyright (c) 2022, NVIDIA CORPORATION. All rights reserved.
 
-from contextlib import contextmanager, nullcontext
-from typing import Optional, List, Union, Callable, Any
+import contextlib
+from typing import Callable, Iterator, List, Optional, Union
 
 import torch
 from torch.autograd.variable import Variable
 from torch.nn.parallel.distributed import DistributedDataParallel as torchDDP
 
+from megatron import core
 from megatron.core import parallel_state
-from megatron.core.pipeline_parallel import p2p_communication
 from megatron.core.enums import ModelType
-from megatron.core.utils import get_attr_wrapped_model, get_model_type
+from megatron.core.pipeline_parallel import p2p_communication
+from megatron.core.utils import get_attr_wrapped_model, get_model_config, get_model_type
 
 # Types
 Shape = Union[List[int], torch.Size]
 
+
 def get_forward_backward_func():
     """Retrieves the appropriate forward_backward function given the
     configuration of parallel_state.
@@ -24,6 +26,10 @@ def get_forward_backward_func():
     world size and virtual pipeline model parallel world size in the
     global parallel_state.
 
+    Note that if using sequence parallelism, the sequence length component of
+    the tensor shape is updated to original_sequence_length /
+    tensor_model_parallel_world_size.
+
     The function returned takes the following arguments:
 
     forward_step_func (required): A function that takes a data
@@ -32,6 +38,13 @@ def get_forward_backward_func():
         take one torch.Tensor and return a torch.Tensor of loss and a
         dictionary of string -> torch.Tensor.
 
+        A third argument, checkpoint_activations_microbatch, indicates
+        that the activations for this microbatch should be
+        checkpointed. A None value for this argument indicates that
+        the default from the configuration should be used. This is
+        used when the
+        num_microbatches_with_partial_activation_checkpoints is used.
+
         For example:
 
         def loss_func(loss_mask, output_tensor):
@@ -54,44 +67,28 @@ def get_forward_backward_func():
 
 
     data_iterator (required): an iterator over the data, will be
-        passed as is to forward_step_func
+        passed as is to forward_step_func. Expected to be a list of
+        iterators in the case of interleaved pipeline parallelism.
 
-    model (required): the actual model. A torch.nn.Module or, in the
-        case or iterleaving, a list of torch.nn.Module
+    model (required): the actual model. Expected to be a list of modules in the case of interleaved
+        pipeline parallelism. Must be a (potentially wrapped) megatron.core.models.MegatronModule.
 
     num_microbatches (int, required):
         The number of microbatches to go through
 
-    dtype (required when using pipeline parallelism): dtype used in
-        p2p communication, usually params_dtype
-
-    tensor_shape (required when using pipeline parallelism): Shape of
-        tensor. The tensor is expected to be 3D and its order of
-        dimension is supposed to be ``(sequence, batch, hidden)``.
+    seq_length (int, required): Sequence length of the current global batch. If this is a dual-stack
+        transformer, this is the encoder's sequence length. This is ignored if variable_seq_lengths
+        in the config is True. Otherwise, each microbatch in the current global batch size must use
+        this sequence length.
 
-    decoder_seq_length (int, required for ModelType.encoder_and_decoder models):
-        Sequence length of the decoder portion, used to determine tensor shapes.
+    micro_batch_size (int, required): The number of sequences in a microbatch.
 
-    grad_scaler (optional, default=None): If using loss scaling,
-        this function should take the loss and return the scaled
-        loss. If None, no function is called on the loss.
+    decoder_seq_length (int, optional): The sequence length for the decoder in a dual-stack
+        transformer. This is ignored for a single-stack transformer.
 
-    sequence_parallel (optional, default=False):
-        Set to :obj:`True` for this function to handle sequence
-        length.  When :obj:`True`, the sequence length on each tensor
-        model parallel rank is updated to
-        :math:`original\_sequence\_length /
-        tensor\_model\_parallel\_world\_size`.
-        TODO: Do we need this? Just roll into tensor_shape arg?
+    forward_only (optional, default = False): Perform only the forward step
 
-    forward_only (optional, default=False): Perform only the forward step
-
-    timers (optional, default=None): TODO
-
-    collect_non_loss_data: TODO
-
-    enable_autocast (optional, default=False): If True, runs the
-        forward_step_func call inside torch.autocast context
+    collect_non_loss_data (optional, bool, default=False): TODO
 
     """
     pipeline_model_parallel_size = parallel_state.get_pipeline_model_parallel_world_size()
@@ -104,24 +101,20 @@ def get_forward_backward_func():
         forward_backward_func = forward_backward_no_pipelining
     return forward_backward_func
 
-def deallocate_output_tensor(out):
+
+def deallocate_output_tensor(out, deallocate_pipeline_outputs=False):
     '''Pseudo-deallocate (i.e., set to scalar) the output tensor's '.data' field.
 
     This method should be called right after the output tensor has been
     sent to the next pipeline stage. At this point, the output tensor is
     only useful for its '.grad_fn' field, and not its '.data'.
     '''
-    if out is None:
+    if (out is None) or (not deallocate_pipeline_outputs):
         return
-    assert isinstance(out, torch.Tensor), \
-        "expected Tensor, found %s." % type(out).__name__
-    assert out._base is None, \
-        "counter-productive to free a view of another tensor."
-    out.data = torch.empty(
-        (1,),
-        device = out.device,
-        dtype = out.dtype,
-    )
+    assert isinstance(out, torch.Tensor), "expected Tensor, found %s." % type(out).__name__
+    assert out._base is None, "counter-productive to free a view of another tensor."
+    out.data = torch.empty((1,), device=out.device, dtype=out.dtype,)
+
 
 def custom_backward(output, grad_output):
     '''Directly call C++ autograd engine.
@@ -132,53 +125,48 @@ def custom_backward(output, grad_output):
     grad have the same shape, while C++'s 'backward' does not.
     '''
 
-    assert output.numel() == 1, \
-        "output should be pseudo-'freed' in schedule, to optimize memory"
-    assert isinstance(output, torch.Tensor), \
-        "output == '%s'." % type(output).__name__
-    assert isinstance(grad_output, (torch.Tensor, type(None))), \
+    assert output.numel() == 1, "output should be pseudo-'freed' in schedule, to optimize memory"
+    assert isinstance(output, torch.Tensor), "output == '%s'." % type(output).__name__
+    assert isinstance(grad_output, (torch.Tensor, type(None))), (
         "grad_output == '%s'." % type(grad_output).__name__
+    )
 
     # Handle scalar output
     if grad_output is None:
         assert output.numel() == 1, "implicit grad requires scalar output."
-        grad_output = torch.ones_like(
-            output,
-            memory_format = torch.preserve_format,
-        )
+        grad_output = torch.ones_like(output, memory_format=torch.preserve_format,)
 
     # Call c++ engine [ see torch/csrc/autograd/python_engine.cpp ]
     Variable._execution_engine.run_backward(
-        tensors = (output,),
-        grad_tensors = (grad_output,),
-        keep_graph = False,
-        create_graph = False,
-        inputs = tuple(),
+        tensors=(output,),
+        grad_tensors=(grad_output,),
+        keep_graph=False,
+        create_graph=False,
+        inputs=tuple(),
         allow_unreachable=True,
         accumulate_grad=True,
     )
 
 
-
-
-
-def forward_step(forward_step_func,
-                 data_iterator,
-                 model,
-                 num_microbatches,
-                 input_tensor,
-                 forward_data_store,
-                 timers,
-                 collect_non_loss_data=False,
-                 enable_autocast=False):
+def forward_step(
+    forward_step_func,
+    data_iterator,
+    model,
+    num_microbatches,
+    input_tensor,
+    forward_data_store,
+    config,
+    collect_non_loss_data=False,
+    checkpoint_activations_microbatch=None,
+):
     """Forward step for passed-in model.
 
     If first stage, input tensor is obtained from data_iterator, otherwise
     passed-in input_tensor is used.
 
     Returns output tensor."""
-    if timers is not None:
-        timers('forward-compute', log_level=2).start()
+    if config.timers is not None:
+        config.timers('forward-compute', log_level=2).start()
 
     unwrap_output_tensor = False
     if not isinstance(input_tensor, list):
@@ -188,9 +176,17 @@ def forward_step(forward_step_func,
     set_input_tensor = get_attr_wrapped_model(model, "set_input_tensor")
     set_input_tensor(input_tensor)
 
-    context_manager = torch.autocast("cuda") if enable_autocast else nullcontext()
+    if config.enable_autocast:
+        context_manager = torch.autocast("cuda", dtype=config.autocast_dtype)
+    else:
+        context_manager = contextlib.nullcontext()
     with context_manager:
-        output_tensor, loss_func = forward_step_func(data_iterator, model)
+        if checkpoint_activations_microbatch is None:
+            output_tensor, loss_func = forward_step_func(data_iterator, model)
+        else:
+            output_tensor, loss_func = forward_step_func(
+                data_iterator, model, checkpoint_activations_microbatch
+            )
 
     if parallel_state.is_pipeline_last_stage():
         if not collect_non_loss_data:
@@ -202,24 +198,24 @@ def forward_step(forward_step_func,
             data = loss_func(output_tensor, non_loss_data=True)
             forward_data_store.append(data)
 
-    if timers is not None:
-        timers('forward-compute').stop()
+    if config.timers is not None:
+        config.timers('forward-compute').stop()
 
     # If T5 model (or other model with encoder and decoder)
     # and in decoder stack, then send encoder_hidden_state
     # downstream as well.
     model_type = get_model_type(model)
-
-    if parallel_state.is_pipeline_stage_after_split() and \
-            model_type == ModelType.encoder_and_decoder:
+    if (
+        parallel_state.is_pipeline_stage_after_split()
+        and model_type == ModelType.encoder_and_decoder
+    ):
         return [output_tensor, input_tensor[-1]]
     if unwrap_output_tensor:
         return output_tensor
     return [output_tensor]
 
 
-def backward_step(grad_scaler, input_tensor, output_tensor,
-                  output_tensor_grad, model_type, timers):
+def backward_step(input_tensor, output_tensor, output_tensor_grad, model_type, config):
     """Backward step through passed-in output tensor.
 
     If last stage, output_tensor_grad is None, otherwise gradient of loss
@@ -232,8 +228,8 @@ def backward_step(grad_scaler, input_tensor, output_tensor,
     # needs to be modified slightly to support arbitrary numbers of skip
     # connections.
 
-    if timers is not None:
-        timers('backward-compute', log_level=2).start()
+    if config.timers is not None:
+        config.timers('backward-compute', log_level=2).start()
 
     # Retain the grad on the input_tensor.
     unwrap_input_tensor_grad = False
@@ -250,9 +246,13 @@ def backward_step(grad_scaler, input_tensor, output_tensor,
         output_tensor_grad = [output_tensor_grad]
 
     # Backward pass.
-    if output_tensor_grad[0] is None and grad_scaler is not None:
-        output_tensor = grad_scaler(output_tensor[0])
-    custom_backward(output_tensor[0], output_tensor_grad[0])
+    if output_tensor_grad[0] is None and config.grad_scale_func is not None:
+        output_tensor[0] = config.grad_scale_func(output_tensor[0])
+
+    if config.deallocate_pipeline_outputs:
+        custom_backward(output_tensor[0], output_tensor_grad[0])
+    else:
+        torch.autograd.backward(output_tensor[0], grad_tensors=output_tensor_grad[0])
 
     # Collect the grad of the input_tensor.
     input_tensor_grad = [None]
@@ -266,42 +266,34 @@ def backward_step(grad_scaler, input_tensor, output_tensor,
 
     # Handle single skip connection if it exists (encoder_hidden_state in
     # model with encoder and decoder).
-    if parallel_state.get_pipeline_model_parallel_world_size() > 1 and \
-            parallel_state.is_pipeline_stage_after_split() and \
-            model_type == ModelType.encoder_and_decoder:
+    if (
+        parallel_state.get_pipeline_model_parallel_world_size() > 1
+        and parallel_state.is_pipeline_stage_after_split()
+        and model_type == ModelType.encoder_and_decoder
+    ):
         if output_tensor_grad[1] is not None:
             input_tensor_grad[-1].add_(output_tensor_grad[1])
     if unwrap_input_tensor_grad:
         input_tensor_grad = input_tensor_grad[0]
 
-    if timers is not None:
-        timers('backward-compute').stop()
+    if config.timers is not None:
+        config.timers('backward-compute').stop()
 
     return input_tensor_grad
 
 
-@contextmanager
-def dummy_handler():
-    try:
-        yield
-    finally:
-        pass
-
-
-def forward_backward_no_pipelining(*,
-                                   forward_step_func,
-                                   data_iterator,
-                                   model: Union[torch.nn.Module, List[torch.nn.Module]],
-                                   num_microbatches: int,
-                                   dtype: Optional[torch.dtype] = None, # unused
-                                   tensor_shape: Optional[Shape] = None, # unused
-                                   decoder_seq_length: Optional[int] = None, # unused
-                                   grad_scaler: Callable = None,
-                                   sequence_parallel: bool = False, # unused
-                                   forward_only: bool = False,
-                                   timers: Callable = None,
-                                   collect_non_loss_data: bool = False,
-                                   enable_autocast: bool = False):
+def forward_backward_no_pipelining(
+    *,
+    forward_step_func,
+    data_iterator: Union[Iterator, List[Iterator]],
+    model: Union[torch.nn.Module, List[torch.nn.Module]],
+    num_microbatches: int,
+    seq_length: int,  # unused
+    micro_batch_size: int,  # unused
+    decoder_seq_length: int = None,  # unused
+    forward_only: bool = False,
+    collect_non_loss_data: bool = False,
+):
     """Run forward and backward passes with no pipeline parallelism
     (no inter-stage communication).
 
@@ -310,57 +302,121 @@ def forward_backward_no_pipelining(*,
 
     See get_forward_backward_func() for argument details
     """
-    assert len(model) == 1
-    model = model[0]
 
-    context_handler = dummy_handler
-    if isinstance(model, torchDDP):
-        context_handler = model.no_sync
+    if isinstance(model, list):
+        assert len(model) == 1, "non-pipeline-parallel schedule does not support model chunking"
+        model = model[0]
+    if isinstance(data_iterator, list):
+        assert (
+            len(data_iterator) == 1
+        ), "non-pipeline-parallel schedule does not support model chunking"
+        data_iterator = data_iterator[0]
+
+    config = get_model_config(model)
+
+    no_sync_func = config.no_sync_func
+    if no_sync_func is None and isinstance(model, torchDDP):
+        no_sync_func = model.no_sync
+    if no_sync_func is None:
+        no_sync_func = contextlib.nullcontext
 
     model_type = get_model_type(model)
 
     forward_data_store = []
     input_tensor, output_tensor_grad = None, None
-    with context_handler():
+    with no_sync_func():
         for i in range(num_microbatches - 1):
-            output_tensor = forward_step(forward_step_func, data_iterator,
-                                         model, num_microbatches, input_tensor, forward_data_store,
-                                         timers, collect_non_loss_data, enable_autocast)
+            output_tensor = forward_step(
+                forward_step_func,
+                data_iterator,
+                model,
+                num_microbatches,
+                input_tensor,
+                forward_data_store,
+                config,
+                collect_non_loss_data,
+            )
             if not forward_only:
-                backward_step(grad_scaler, input_tensor, output_tensor,
-                              output_tensor_grad, model_type, timers)
+                backward_step(input_tensor, output_tensor, output_tensor_grad, model_type, config)
 
     # Run computation for last microbatch out of context handler (want to
     # synchronize gradients).
-    output_tensor = forward_step(forward_step_func, data_iterator,
-                                 model, num_microbatches, input_tensor, forward_data_store,
-                                 timers, collect_non_loss_data, enable_autocast)
+    output_tensor = forward_step(
+        forward_step_func,
+        data_iterator,
+        model,
+        num_microbatches,
+        input_tensor,
+        forward_data_store,
+        config,
+        collect_non_loss_data,
+    )
 
     if not forward_only:
-        backward_step(grad_scaler, input_tensor, output_tensor,
-                      output_tensor_grad, model_type, timers)
+        backward_step(input_tensor, output_tensor, output_tensor_grad, model_type, config)
 
     return forward_data_store
 
 
-def forward_backward_pipelining_with_interleaving(*,
-                                                  forward_step_func,
-                                                  data_iterator,
-                                                  model: Union[torch.nn.Module, List[torch.nn.Module]],
-                                                  num_microbatches: int,
-                                                  dtype: torch.dtype,
-                                                  tensor_shape: Shape,
-                                                  decoder_seq_length: Optional[int] = None,
-                                                  grad_scaler: Callable = None,
-                                                  sequence_parallel: bool = False,
-                                                  forward_only: bool = False,
-                                                  timers: Callable = None,
-                                                  collect_non_loss_data: bool = False,
-                                                  enable_autocast: bool = False):
+def forward_backward_pipelining_with_interleaving(
+    *,
+    forward_step_func,
+    data_iterator: Union[Iterator, List[Iterator]],
+    model: Union[torch.nn.Module, List[torch.nn.Module]],
+    num_microbatches: int,
+    seq_length: int,
+    micro_batch_size: int,
+    decoder_seq_length: int = None,
+    forward_only: bool = False,
+    collect_non_loss_data: bool = False,
+):
     """Run interleaved 1F1B schedule (model split into model chunks), with
     communication between pipeline stages as needed.
 
     Returns dictionary with losses if the last stage, empty dict otherwise."""
+    assert isinstance(model, list), "interleaved pipeline parallelism expected model chunking"
+    assert all(isinstance(chunk, torch.nn.Module) for chunk in model), "invalid model chunking"
+    assert isinstance(
+        data_iterator, list
+    ), "interleaved pipeline parallelism expected each model chunk to have a data iterator"
+
+    config = get_model_config(model[0])
+    if config.overlap_p2p_comm and config.batch_p2p_comm:
+        raise ValueError("Can not use both overlap_p2p_comm and batch_p2p_comm")
+
+    # Disable async grad reductions
+    no_sync_func = config.no_sync_func
+    if no_sync_func is None and all(isinstance(chunk, torchDDP) for chunk in model):
+
+        def multi_no_sync():
+            stack = contextlib.ExitStack()
+            for chunk in model:
+                stack.enter_context(chunk.no_sync())
+            return stack
+
+        no_sync_func = multi_no_sync
+    if no_sync_func is None:
+        no_sync_func = contextlib.nullcontext
+    no_sync_context = None
+
+    def disable_grad_sync():
+        """Disable asynchronous grad reductions"""
+        nonlocal no_sync_context
+        if no_sync_context is None:
+            no_sync_context = no_sync_func()
+            no_sync_context.__enter__()
+
+    def enable_grad_sync():
+        """Enable asynchronous grad reductions"""
+        nonlocal no_sync_context
+        if no_sync_context is not None:
+            no_sync_context.__exit__(None, None, None)
+            no_sync_context = None
+
+    disable_grad_sync()
+
+    # Model chunk IDs with synchronized grads
+    synchronized_model_chunks = set()
 
     input_tensors = [[] for _ in range(len(model))]
     output_tensors = [[] for _ in range(len(model))]
@@ -381,17 +437,15 @@ def forward_backward_pipelining_with_interleaving(*,
     if model_type == ModelType.encoder_and_decoder:
         raise RuntimeError("Interleaving is not supported with an encoder and decoder model.")
 
-    if decoder_seq_length is not None and decoder_seq_length != tensor_shape[0]:
-        raise RuntimeError("Interleaving is not supported with a different decoder sequence length.")
-
-    if sequence_parallel:
-        seq_length, batch_size, hidden = tensor_shape
-        tensor_shape = (
-            seq_length // parallel_state.get_tensor_model_parallel_world_size(),
-            batch_size,
-            hidden,
+    if decoder_seq_length is not None and decoder_seq_length != seq_length:
+        raise RuntimeError(
+            "Interleaving is not supported with a different decoder sequence length."
         )
 
+    tensor_shape = [seq_length, micro_batch_size, config.hidden_size]
+    if config.sequence_parallel:
+        tensor_shape[0] = tensor_shape[0] // parallel_state.get_tensor_model_parallel_world_size()
+
     # Compute number of warmup and remaining microbatches.
     num_model_chunks = len(model)
     total_num_microbatches = num_microbatches * num_model_chunks
@@ -409,45 +463,96 @@ def forward_backward_pipelining_with_interleaving(*,
             num_warmup_microbatches = total_num_microbatches
             all_warmup_microbatches = True
         else:
-            num_warmup_microbatches = \
-                (pipeline_parallel_size - pipeline_parallel_rank - 1) * 2
-            num_warmup_microbatches += (
-                num_model_chunks - 1) * pipeline_parallel_size
-            num_warmup_microbatches = min(num_warmup_microbatches,
-                                          total_num_microbatches)
-    num_microbatches_remaining = \
-        total_num_microbatches - num_warmup_microbatches
+            num_warmup_microbatches = (pipeline_parallel_size - pipeline_parallel_rank - 1) * 2
+            num_warmup_microbatches += (num_model_chunks - 1) * pipeline_parallel_size
+            num_warmup_microbatches = min(num_warmup_microbatches, total_num_microbatches)
+    num_microbatches_remaining = total_num_microbatches - num_warmup_microbatches
+
+    # Checkpoint the activations of partial Transformer layers in a number of micro-batches
+    # within the maximum outstanding micro-batch backpropagations.
+    # Micro-batches with the ids less than 'num_microbatches_with_partial_activation_checkpoints'
+    # checkpoint partial Transformer layers (or skip checkpointing) and
+    # the rest of micro-batches within a window of micro-batches checkpoint
+    # all Transformer layers. The window of micro-batches is set by the maximum
+    # outstanding backpropagations and becomes smaller at later pipeline stages.
+    # Please refer the appendix C in https://arxiv.org/pdf/2205.05198.pdf
+    max_outstanding_backprops = None
+    if config.num_microbatches_with_partial_activation_checkpoints is not None:
+        max_outstanding_backprops = num_warmup_microbatches + 1
+
+    # Synchronize params for first two model chunks
+    if config.param_sync_func is not None:
+        config.param_sync_func(model[0].parameters())
+        config.param_sync_func(model[1].parameters())
 
     def get_model_chunk_id(microbatch_id, forward):
         """Helper method to get the model chunk ID given the iteration number."""
         microbatch_id_in_group = microbatch_id % (pipeline_parallel_size * num_model_chunks)
         model_chunk_id = microbatch_id_in_group // pipeline_parallel_size
         if not forward:
-            model_chunk_id = (num_model_chunks - model_chunk_id - 1)
+            model_chunk_id = num_model_chunks - model_chunk_id - 1
         return model_chunk_id
 
-    def forward_step_helper(microbatch_id):
+    def is_first_microbatch_for_model_chunk(microbatch_id: int) -> bool:
+        """Check if an iteration is the first for a model chunk."""
+        microbatch_group_size = pipeline_parallel_size * num_model_chunks
+        num_microbatch_groups = total_num_microbatches // microbatch_group_size
+        microbatch_group_id = microbatch_id // microbatch_group_size
+        microbatch_id_in_group = microbatch_id % microbatch_group_size
+        if microbatch_group_id == 0:
+            return microbatch_id_in_group % pipeline_parallel_size == 0
+        else:
+            return False
+
+    def is_last_microbatch_for_model_chunk(microbatch_id: int) -> bool:
+        """Check if an iteration is the last for a model chunk."""
+        microbatch_group_size = pipeline_parallel_size * num_model_chunks
+        num_microbatch_groups = total_num_microbatches // microbatch_group_size
+        microbatch_group_id = microbatch_id // microbatch_group_size
+        microbatch_id_in_group = microbatch_id % microbatch_group_size
+        if microbatch_group_id == num_microbatch_groups - 1:
+            return microbatch_id_in_group % pipeline_parallel_size == pipeline_parallel_size - 1
+        else:
+            return False
+
+    def forward_step_helper(microbatch_id, checkpoint_activations_microbatch):
         """Helper method to run forward step with model split into chunks
         (run set_virtual_pipeline_model_parallel_rank() before calling
         forward_step())."""
         model_chunk_id = get_model_chunk_id(microbatch_id, forward=True)
         parallel_state.set_virtual_pipeline_model_parallel_rank(model_chunk_id)
 
+        # launch param synchronization for next model chunk
+        # Note: Asynchronous communication tends to slow down compute.
+        # To reduce idling from mismatched microbatch times, we launch
+        # asynchronous communication at the same time across the
+        # pipeline-parallel group.
+        if config.param_sync_func is not None:
+            param_sync_microbatch_id = microbatch_id + pipeline_parallel_rank
+            if (
+                param_sync_microbatch_id < total_num_microbatches
+                and is_first_microbatch_for_model_chunk(param_sync_microbatch_id)
+            ):
+                param_sync_chunk_id = get_model_chunk_id(param_sync_microbatch_id, forward=True) + 1
+                if 1 < param_sync_chunk_id < num_model_chunks:
+                    config.param_sync_func(model[param_sync_chunk_id].parameters())
+
         # forward step
         if parallel_state.is_pipeline_first_stage():
-            if len(input_tensors[model_chunk_id]) == \
-                    len(output_tensors[model_chunk_id]):
+            if len(input_tensors[model_chunk_id]) == len(output_tensors[model_chunk_id]):
                 input_tensors[model_chunk_id].append(None)
         input_tensor = input_tensors[model_chunk_id][-1]
-        output_tensor = forward_step(forward_step_func,
-                                     data_iterator[model_chunk_id],
-                                     model[model_chunk_id],
-                                     num_microbatches,
-                                     input_tensor,
-                                     forward_data_store,
-                                     timers,
-                                     collect_non_loss_data,
-                                     enable_autocast)
+        output_tensor = forward_step(
+            forward_step_func,
+            data_iterator[model_chunk_id],
+            model[model_chunk_id],
+            num_microbatches,
+            input_tensor,
+            forward_data_store,
+            config,
+            collect_non_loss_data,
+            checkpoint_activations_microbatch,
+        )
         output_tensors[model_chunk_id].append(output_tensor)
 
         # if forward-only, no need to save tensors for a backward pass
@@ -464,31 +569,65 @@ def forward_backward_pipelining_with_interleaving(*,
         model_chunk_id = get_model_chunk_id(microbatch_id, forward=False)
         parallel_state.set_virtual_pipeline_model_parallel_rank(model_chunk_id)
 
+        # launch grad synchronization (default)
+        if config.grad_sync_func is None and is_last_microbatch_for_model_chunk(microbatch_id):
+            enable_grad_sync()
+            synchronized_model_chunks.add(model_chunk_id)
+
         if parallel_state.is_pipeline_last_stage():
             if len(output_tensor_grads[model_chunk_id]) == 0:
                 output_tensor_grads[model_chunk_id].append(None)
         input_tensor = input_tensors[model_chunk_id].pop(0)
         output_tensor = output_tensors[model_chunk_id].pop(0)
         output_tensor_grad = output_tensor_grads[model_chunk_id].pop(0)
-        input_tensor_grad = \
-            backward_step(grad_scaler,
-                          input_tensor,
-                          output_tensor,
-                          output_tensor_grad,
-                          model_type,
-                          timers)
+        input_tensor_grad = backward_step(
+            input_tensor, output_tensor, output_tensor_grad, model_type, config
+        )
+
+        # launch grad synchronization (custom grad sync)
+        # Note: Asynchronous communication tends to slow down compute.
+        # To reduce idling from mismatched microbatch times, we launch
+        # asynchronous communication at the same time across the
+        # pipeline-parallel group.
+        if config.grad_sync_func is not None:
+            grad_sync_microbatch_id = microbatch_id - pipeline_parallel_rank
+            if grad_sync_microbatch_id >= 0 and is_last_microbatch_for_model_chunk(
+                grad_sync_microbatch_id
+            ):
+                grad_sync_chunk_id = get_model_chunk_id(grad_sync_microbatch_id, forward=False)
+                enable_grad_sync()
+                config.grad_sync_func(model[grad_sync_chunk_id].parameters())
+                synchronized_model_chunks.add(grad_sync_chunk_id)
+        disable_grad_sync()
 
         return input_tensor_grad
 
     # Run warmup forward passes.
     parallel_state.set_virtual_pipeline_model_parallel_rank(0)
-    input_tensors[0].append(
-        p2p_communication.recv_forward(tensor_shape, dtype, timers=timers))
+    input_tensors[0].append(p2p_communication.recv_forward(tensor_shape, config))
+
+    fwd_wait_handles = None
+    bwd_wait_handles = None
+
     for k in range(num_warmup_microbatches):
-        output_tensor = forward_step_helper(k)
+
+        if fwd_wait_handles is not None:
+            for req in fwd_wait_handles:
+                req.wait()
+
+        # Decide to checkpoint all layers' activations of the current micro-batch
+        if max_outstanding_backprops is not None:
+            checkpoint_activations_microbatch = (
+                k % max_outstanding_backprops
+                >= config.num_microbatches_with_partial_activation_checkpoints
+            )
+        else:
+            checkpoint_activations_microbatch = None
+
+        output_tensor = forward_step_helper(k, checkpoint_activations_microbatch)
 
         # Determine if tensor should be received from previous stage.
-        next_forward_model_chunk_id = get_model_chunk_id(k+1, forward=True)
+        next_forward_model_chunk_id = get_model_chunk_id(k + 1, forward=True)
         recv_prev = True
         if parallel_state.is_pipeline_first_stage(ignore_virtual=True):
             if next_forward_model_chunk_id == 0:
@@ -502,108 +641,255 @@ def forward_backward_pipelining_with_interleaving(*,
 
         # Send and receive tensors as appropriate (send tensors computed
         # in this iteration; receive tensors for next iteration).
-        if k == (num_warmup_microbatches - 1) and not forward_only and \
-                not all_warmup_microbatches:
-            input_tensor_grad = None
-            recv_next = True
-            if parallel_state.is_pipeline_last_stage(ignore_virtual=True):
-                recv_next = False
-            input_tensor, output_tensor_grad = \
-                p2p_communication.send_forward_backward_recv_forward_backward(
-                        output_tensor, input_tensor_grad,
-                        recv_prev=recv_prev, recv_next=recv_next,
-                        tensor_shape=tensor_shape, dtype=dtype,
-                        timers=timers)
-            output_tensor_grads[num_model_chunks-1].append(output_tensor_grad)
+        if not config.overlap_p2p_comm:
+            if (
+                k == (num_warmup_microbatches - 1)
+                and not forward_only
+                and not all_warmup_microbatches
+            ):
+                input_tensor_grad = None
+                recv_next = True
+                if parallel_state.is_pipeline_last_stage(ignore_virtual=True):
+                    recv_next = False
+                (
+                    input_tensor,
+                    output_tensor_grad,
+                ) = p2p_communication.send_forward_backward_recv_forward_backward(
+                    output_tensor,
+                    input_tensor_grad,
+                    recv_prev=recv_prev,
+                    recv_next=recv_next,
+                    tensor_shape=tensor_shape,
+                    config=config,
+                )
+                output_tensor_grads[num_model_chunks - 1].append(output_tensor_grad)
+            else:
+                input_tensor = p2p_communication.send_forward_recv_forward(
+                    output_tensor, recv_prev=recv_prev, tensor_shape=tensor_shape, config=config
+                )
+            input_tensors[next_forward_model_chunk_id].append(input_tensor)
         else:
-            input_tensor = \
-                p2p_communication.send_forward_recv_forward(
-                    output_tensor, recv_prev=recv_prev,
-                    tensor_shape=tensor_shape, dtype=dtype,
-                    timers=timers)
-        input_tensors[next_forward_model_chunk_id].append(input_tensor)
-        deallocate_output_tensor(output_tensor)
+            input_tensor, fwd_wait_handles = p2p_communication.send_forward_recv_forward(
+                output_tensor,
+                recv_prev=recv_prev,
+                tensor_shape=tensor_shape,
+                config=config,
+                overlap_p2p_comm=True,
+            )
+
+            if (
+                k == (num_warmup_microbatches - 1)
+                and not forward_only
+                and not all_warmup_microbatches
+            ):
+                input_tensor_grad = None
+                recv_next = True
+                if parallel_state.is_pipeline_last_stage(ignore_virtual=True):
+                    recv_next = False
+
+                (
+                    output_tensor_grad,
+                    bwd_wait_handles,
+                ) = p2p_communication.send_backward_recv_backward(
+                    input_tensor_grad,
+                    recv_next=recv_next,
+                    tensor_shape=tensor_shape,
+                    config=config,
+                    overlap_p2p_comm=True,
+                )
+
+                output_tensor_grads[num_model_chunks - 1].append(output_tensor_grad)
+            input_tensors[next_forward_model_chunk_id].append(input_tensor)
+
+        deallocate_output_tensor(output_tensor, config.deallocate_pipeline_outputs)
 
     # Run 1F1B in steady state.
     for k in range(num_microbatches_remaining):
         # Forward pass.
         forward_k = k + num_warmup_microbatches
-        output_tensor = forward_step_helper(forward_k)
 
-        # Backward pass.
-        backward_k = k
-        input_tensor_grad = backward_step_helper(backward_k)
+        # Decide to checkpoint all layers' activations of the current micro-batch
+        if max_outstanding_backprops is not None:
+            checkpoint_activations_microbatch = (
+                forward_k % max_outstanding_backprops
+                >= config.num_microbatches_with_partial_activation_checkpoints
+            )
+        else:
+            checkpoint_activations_microbatch = None
+
+        if config.overlap_p2p_comm:
+            if fwd_wait_handles is not None:
+                for req in fwd_wait_handles:
+                    req.wait()
+
+            deallocate_output_tensor(output_tensor, config.deallocate_pipeline_outputs)
+
+            output_tensor = forward_step_helper(forward_k, checkpoint_activations_microbatch)
+
+            # Determine if current stage has anything to send in either direction,
+            # otherwise set tensor to None.
+            forward_model_chunk_id = get_model_chunk_id(forward_k, forward=True)
+            parallel_state.set_virtual_pipeline_model_parallel_rank(forward_model_chunk_id)
+
+            # Last virtual stage no activation tensor to send
+            if parallel_state.is_pipeline_last_stage():
+                output_tensor = None
+
+            # Determine if peers are sending, and where in data structure to put
+            # received tensors.
+            recv_prev = True
+            if parallel_state.is_pipeline_first_stage(ignore_virtual=True):
+                # First stage is ahead of last stage by (pipeline_parallel_size - 1).
+                next_forward_model_chunk_id = get_model_chunk_id(
+                    forward_k - (pipeline_parallel_size - 1), forward=True
+                )
+                if next_forward_model_chunk_id == (num_model_chunks - 1):
+                    recv_prev = False
+                next_forward_model_chunk_id += 1
+            else:
+                next_forward_model_chunk_id = get_model_chunk_id(forward_k + 1, forward=True)
 
-        # Send output_tensor and input_tensor_grad, receive input_tensor
-        # and output_tensor_grad.
+            # If last iteration, don't receive; we already received one extra
+            # before the start of the for loop.
+            if k == (num_microbatches_remaining - 1):
+                recv_prev = False
 
-        # Determine if current stage has anything to send in either direction,
-        # otherwise set tensor to None.
-        forward_model_chunk_id = get_model_chunk_id(forward_k, forward=True)
-        parallel_state.set_virtual_pipeline_model_parallel_rank(forward_model_chunk_id)
-        if parallel_state.is_pipeline_last_stage():
-            output_tensor = None
+            # Send activation tensor to the next stage and receive activation tensor from the
+            # previous stage
+            input_tensor, fwd_wait_handles = p2p_communication.send_forward_recv_forward(
+                output_tensor,
+                recv_prev=recv_prev,
+                tensor_shape=tensor_shape,
+                config=config,
+                overlap_p2p_comm=True,
+            )
+            # assert fwd_wait_handles is not None
+
+            if bwd_wait_handles is not None:
+                for req in bwd_wait_handles:
+                    req.wait()
+
+            # Backward pass.
+            backward_k = k
+            input_tensor_grad = backward_step_helper(backward_k)
+
+            backward_model_chunk_id = get_model_chunk_id(backward_k, forward=False)
+            parallel_state.set_virtual_pipeline_model_parallel_rank(backward_model_chunk_id)
+
+            # First virtual stage no activation gradient tensor to send
+            if parallel_state.is_pipeline_first_stage():
+                input_tensor_grad = None
+
+            # Determine if the current virtual stage has an activation gradient tensor to receive
+            recv_next = True
+            if parallel_state.is_pipeline_last_stage(ignore_virtual=True):
+                # Last stage is ahead of first stage by (pipeline_parallel_size - 1).
+                next_backward_model_chunk_id = get_model_chunk_id(
+                    backward_k - (pipeline_parallel_size - 1), forward=False
+                )
+                if next_backward_model_chunk_id == 0:
+                    recv_next = False
+                next_backward_model_chunk_id -= 1
+            else:
+                next_backward_model_chunk_id = get_model_chunk_id(backward_k + 1, forward=False)
+
+            output_tensor_grad, bwd_wait_handles = p2p_communication.send_backward_recv_backward(
+                input_tensor_grad,
+                recv_next=recv_next,
+                tensor_shape=tensor_shape,
+                config=config,
+                overlap_p2p_comm=True,
+            )
+
+        else:  # no p2p overlap
+            output_tensor = forward_step_helper(forward_k, checkpoint_activations_microbatch)
+
+            # Backward pass.
+            backward_k = k
+            input_tensor_grad = backward_step_helper(backward_k)
+
+            # Send output_tensor and input_tensor_grad, receive input_tensor
+            # and output_tensor_grad.
+
+            # Determine if current stage has anything to send in either direction,
+            # otherwise set tensor to None.
+            forward_model_chunk_id = get_model_chunk_id(forward_k, forward=True)
+            parallel_state.set_virtual_pipeline_model_parallel_rank(forward_model_chunk_id)
+            if parallel_state.is_pipeline_last_stage():
+                output_tensor = None
+
+            backward_model_chunk_id = get_model_chunk_id(backward_k, forward=False)
+            parallel_state.set_virtual_pipeline_model_parallel_rank(backward_model_chunk_id)
+            if parallel_state.is_pipeline_first_stage():
+                input_tensor_grad = None
+
+            # Determine if peers are sending, and where in data structure to put
+            # received tensors.
+            recv_prev = True
+            if parallel_state.is_pipeline_first_stage(ignore_virtual=True):
+                # First stage is ahead of last stage by (pipeline_parallel_size - 1).
+                next_forward_model_chunk_id = get_model_chunk_id(
+                    forward_k - (pipeline_parallel_size - 1), forward=True
+                )
+                if next_forward_model_chunk_id == (num_model_chunks - 1):
+                    recv_prev = False
+                next_forward_model_chunk_id += 1
+            else:
+                next_forward_model_chunk_id = get_model_chunk_id(forward_k + 1, forward=True)
 
-        backward_model_chunk_id = get_model_chunk_id(backward_k, forward=False)
-        parallel_state.set_virtual_pipeline_model_parallel_rank(backward_model_chunk_id)
-        if parallel_state.is_pipeline_first_stage():
-            input_tensor_grad = None
+            recv_next = True
+            if parallel_state.is_pipeline_last_stage(ignore_virtual=True):
+                # Last stage is ahead of first stage by (pipeline_parallel_size - 1).
+                next_backward_model_chunk_id = get_model_chunk_id(
+                    backward_k - (pipeline_parallel_size - 1), forward=False
+                )
+                if next_backward_model_chunk_id == 0:
+                    recv_next = False
+                next_backward_model_chunk_id -= 1
+            else:
+                next_backward_model_chunk_id = get_model_chunk_id(backward_k + 1, forward=False)
 
-        # Determine if peers are sending, and where in data structure to put
-        # received tensors.
-        recv_prev = True
-        if parallel_state.is_pipeline_first_stage(ignore_virtual=True):
-            # First stage is ahead of last stage by (pipeline_parallel_size - 1).
-            next_forward_model_chunk_id = get_model_chunk_id(
-                forward_k - (pipeline_parallel_size - 1), forward=True)
-            if next_forward_model_chunk_id == (num_model_chunks - 1):
+            # If last iteration, don't receive; we already received one extra
+            # before the start of the for loop.
+            if k == (num_microbatches_remaining - 1):
                 recv_prev = False
-            next_forward_model_chunk_id += 1
-        else:
-            next_forward_model_chunk_id = get_model_chunk_id(forward_k + 1,
-                                                             forward=True)
-
-        recv_next = True
-        if parallel_state.is_pipeline_last_stage(ignore_virtual=True):
-            # Last stage is ahead of first stage by (pipeline_parallel_size - 1).
-            next_backward_model_chunk_id = get_model_chunk_id(
-                backward_k - (pipeline_parallel_size - 1), forward=False)
-            if next_backward_model_chunk_id == 0:
-                recv_next = False
-            next_backward_model_chunk_id -= 1
-        else:
-            next_backward_model_chunk_id = get_model_chunk_id(backward_k + 1,
-                                                              forward=False)
 
-        # If last iteration, don't receive; we already received one extra
-        # before the start of the for loop.
-        if k == (num_microbatches_remaining - 1):
-            recv_prev = False
-
-        # Communicate tensors.
-        input_tensor, output_tensor_grad = \
-            p2p_communication.send_forward_backward_recv_forward_backward(
-                    output_tensor, input_tensor_grad,
-                    recv_prev=recv_prev, recv_next=recv_next,
-                    tensor_shape=tensor_shape, dtype=dtype, timers=timers)
-        deallocate_output_tensor(output_tensor)
+            # Communicate tensors.
+            (
+                input_tensor,
+                output_tensor_grad,
+            ) = p2p_communication.send_forward_backward_recv_forward_backward(
+                output_tensor,
+                input_tensor_grad,
+                recv_prev=recv_prev,
+                recv_next=recv_next,
+                tensor_shape=tensor_shape,
+                config=config,
+            )
+            deallocate_output_tensor(output_tensor, config.deallocate_pipeline_outputs)
 
         # Put input_tensor and output_tensor_grad in data structures in the
         # right location.
         if recv_prev:
             input_tensors[next_forward_model_chunk_id].append(input_tensor)
         if recv_next:
-            output_tensor_grads[next_backward_model_chunk_id].append(
-                output_tensor_grad)
+            output_tensor_grads[next_backward_model_chunk_id].append(output_tensor_grad)
+
+    deallocate_output_tensor(output_tensor, config.deallocate_pipeline_outputs)
 
     # Run cooldown backward passes (flush out pipeline).
     if not forward_only:
+        if config.overlap_p2p_comm and bwd_wait_handles is not None:
+            for wait_handle in bwd_wait_handles:
+                wait_handle.wait()
+
         if all_warmup_microbatches:
-            output_tensor_grads[num_model_chunks-1].append(
-                p2p_communication.recv_backward(tensor_shape, dtype=dtype, timers=timers))
+            output_tensor_grads[num_model_chunks - 1].append(
+                p2p_communication.recv_backward(tensor_shape, config=config)
+            )
         for k in range(num_microbatches_remaining, total_num_microbatches):
             input_tensor_grad = backward_step_helper(k)
-            next_backward_model_chunk_id = get_model_chunk_id(k+1, forward=False)
+            next_backward_model_chunk_id = get_model_chunk_id(k + 1, forward=False)
             recv_next = True
             if parallel_state.is_pipeline_last_stage(ignore_virtual=True):
                 if next_backward_model_chunk_id == (num_model_chunks - 1):
@@ -612,18 +898,33 @@ def forward_backward_pipelining_with_interleaving(*,
                 recv_next = False
             output_tensor_grads[next_backward_model_chunk_id].append(
                 p2p_communication.send_backward_recv_backward(
-                    input_tensor_grad, recv_next=recv_next,
-                    tensor_shape=tensor_shape, dtype=dtype,
-                    timers=timers))
+                    input_tensor_grad, recv_next=recv_next, tensor_shape=tensor_shape, config=config
+                )
+            )
+
+    # Launch any remaining grad reductions
+    enable_grad_sync()
+    if config.grad_sync_func is not None:
+        params = []
+        for model_chunk_id in range(num_model_chunks):
+            if model_chunk_id not in synchronized_model_chunks:
+                params.extend(model[model_chunk_id].parameters())
+                synchronized_model_chunks.add(model_chunk_id)
+        if params:
+            config.grad_sync_func(params)
 
     return forward_data_store
 
-def get_tensor_shapes(*,
-                      rank: int,
-                      model_type: ModelType,
-                      tensor_shape: Shape,
-                      decoder_seq_length: int,
-                      sequence_parallel: bool):
+
+def get_tensor_shapes(
+    *,
+    rank: int,
+    model_type: ModelType,
+    seq_length: int,
+    micro_batch_size: int,
+    decoder_seq_length: int,
+    config,
+):
     # Determine right tensor sizes (based on position of rank with respect to split
     # rank) and model size.
     # Send two tensors if model is T5 and rank is in decoder stage:
@@ -634,71 +935,63 @@ def get_tensor_shapes(*,
     # Otherwise, send one tensor (pre-transpose).
     tensor_shapes = []
 
-    assert (
-        len(tensor_shape) == 3
-    ), f"`tensor_shape` should be [sequence_length, micro_batch_size, hidden_size] but {tensor_shape}"
-
-    seq_length, micro_batch_size, hidden_size = tensor_shape
-
-    if sequence_parallel:
+    if config.sequence_parallel:
         seq_length = seq_length // parallel_state.get_tensor_model_parallel_world_size()
+        if model_type == ModelType.encoder_and_decoder:
+            decoder_seq_length = (
+                decoder_seq_length // parallel_state.get_tensor_model_parallel_world_size()
+            )
 
     if model_type == ModelType.encoder_and_decoder:
-        if sequence_parallel:
-            decoder_seq_length = decoder_seq_length // parallel_state.get_tensor_model_parallel_world_size()
-
         if parallel_state.is_pipeline_stage_before_split(rank):
-            tensor_shapes.append((seq_length, micro_batch_size, hidden_size))
+            tensor_shapes.append((seq_length, micro_batch_size, config.hidden_size))
         else:
-            tensor_shapes.append((decoder_seq_length, micro_batch_size, hidden_size))
-            tensor_shapes.append((seq_length, micro_batch_size, hidden_size))
+            tensor_shapes.append((decoder_seq_length, micro_batch_size, config.hidden_size))
+            tensor_shapes.append((seq_length, micro_batch_size, config.hidden_size))
     else:
-        tensor_shapes.append((seq_length, micro_batch_size, hidden_size))
+        tensor_shapes.append((seq_length, micro_batch_size, config.hidden_size))
     return tensor_shapes
 
 
-
-def recv_forward(tensor_shapes, dtype, timers):
+def recv_forward(tensor_shapes, config):
     input_tensors = []
     for tensor_shape in tensor_shapes:
         if tensor_shape is None:
             input_tensors.append(None)
         else:
-            input_tensors.append(p2p_communication.recv_forward(tensor_shape, dtype,
-                                                                timers=timers))
+            input_tensors.append(p2p_communication.recv_forward(tensor_shape, config))
     return input_tensors
 
 
-def recv_backward(tensor_shapes, dtype, timers):
+def recv_backward(tensor_shapes, config):
     output_tensor_grads = []
     for tensor_shape in tensor_shapes:
         if tensor_shape is None:
             output_tensor_grads.append(None)
         else:
-            output_tensor_grads.append(p2p_communication.recv_backward(tensor_shape, dtype,
-                                                                       timers=timers))
+            output_tensor_grads.append(p2p_communication.recv_backward(tensor_shape, config))
     return output_tensor_grads
 
 
-def send_forward(output_tensors, tensor_shapes, timers):
+def send_forward(output_tensors, tensor_shapes, config):
     if not isinstance(output_tensors, list):
         output_tensors = [output_tensors]
     for (output_tensor, tensor_shape) in zip(output_tensors, tensor_shapes):
         if tensor_shape is None:
             continue
-        p2p_communication.send_forward(output_tensor, timers=timers)
+        p2p_communication.send_forward(output_tensor, config)
 
 
-def send_backward(input_tensor_grads, tensor_shapes, timers):
+def send_backward(input_tensor_grads, tensor_shapes, config):
     if not isinstance(input_tensor_grads, list):
         input_tensor_grads = [input_tensor_grads]
     for (input_tensor_grad, tensor_shape) in zip(input_tensor_grads, tensor_shapes):
         if tensor_shape is None:
             continue
-        p2p_communication.send_backward(input_tensor_grad, timers=timers)
+        p2p_communication.send_backward(input_tensor_grad, config)
 
 
-def send_forward_recv_backward(output_tensors, tensor_shapes, dtype, timers):
+def send_forward_recv_backward(output_tensors, tensor_shapes, config):
     if not isinstance(output_tensors, list):
         output_tensors = [output_tensors]
     output_tensor_grads = []
@@ -707,12 +1000,13 @@ def send_forward_recv_backward(output_tensors, tensor_shapes, dtype, timers):
             output_tensor_grads.append(None)
             continue
         output_tensor_grad = p2p_communication.send_forward_recv_backward(
-                output_tensor, tensor_shape, dtype, timers=timers)
+            output_tensor, tensor_shape, config
+        )
         output_tensor_grads.append(output_tensor_grad)
     return output_tensor_grads
 
 
-def send_backward_recv_forward(input_tensor_grads, tensor_shapes, dtype, timers):
+def send_backward_recv_forward(input_tensor_grads, tensor_shapes, config):
     if not isinstance(input_tensor_grads, list):
         input_tensor_grads = [input_tensor_grads]
     input_tensors = []
@@ -721,56 +1015,110 @@ def send_backward_recv_forward(input_tensor_grads, tensor_shapes, dtype, timers)
             input_tensors.append(None)
             continue
         input_tensor = p2p_communication.send_backward_recv_forward(
-                input_tensor_grad, tensor_shape, dtype, timers=timers)
+            input_tensor_grad, tensor_shape, config
+        )
         input_tensors.append(input_tensor)
     return input_tensors
 
 
-def forward_backward_pipelining_without_interleaving(*,
-                                                     forward_step_func,
-                                                     data_iterator,
-                                                     model: Union[torch.nn.Module, List[torch.nn.Module]],
-                                                     num_microbatches: int,
-                                                     dtype: torch.dtype,
-                                                     tensor_shape: Shape,
-                                                     decoder_seq_length: Optional[int] = None,
-                                                     grad_scaler: Callable = None,
-                                                     sequence_parallel: bool = False,
-                                                     forward_only: bool = False,
-                                                     timers: Callable = None,
-                                                     collect_non_loss_data: bool = False,
-                                                     enable_autocast: bool = False):
+def forward_backward_pipelining_without_interleaving(
+    *,
+    forward_step_func,
+    data_iterator: Union[Iterator, List[Iterator]],
+    model: Union[torch.nn.Module, List[torch.nn.Module]],
+    num_microbatches: int,
+    seq_length: int,
+    micro_batch_size: int,
+    decoder_seq_length: int = None,
+    forward_only: bool = False,
+    collect_non_loss_data: bool = False,
+):
     """Run non-interleaved 1F1B schedule, with communication between pipeline
     stages.
 
     Returns dictionary with losses if the last stage, empty dict otherwise."""
 
-    assert len(model) == 1
-    model = model[0]
+    if isinstance(model, list):
+        assert (
+            len(model) == 1
+        ), "non-interleaved pipeline parallelism does not support model chunking"
+        model = model[0]
+    if isinstance(data_iterator, list):
+        assert (
+            len(data_iterator) == 1
+        ), "non-pipeline-parallel schedule does not support model chunking"
+        data_iterator = data_iterator[0]
+
+    config = get_model_config(model)
+    if config.overlap_p2p_comm:
+        raise ValueError(
+            "Non-interleaved pipeline parallelism does not support overlapping p2p communication"
+        )
+
+    # Disable async grad reductions
+    no_sync_func = config.no_sync_func
+    if no_sync_func is None and isinstance(model, torchDDP):
+        no_sync_func = model.no_sync
+    if no_sync_func is None:
+        no_sync_func = contextlib.nullcontext
+    no_sync_context = None
+
+    def disable_grad_sync():
+        """Disable asynchronous grad reductions"""
+        nonlocal no_sync_context
+        if no_sync_context is None:
+            no_sync_context = no_sync_func()
+            no_sync_context.__enter__()
+
+    def enable_grad_sync():
+        """Enable asynchronous grad reductions"""
+        nonlocal no_sync_context
+        if no_sync_context is not None:
+            no_sync_context.__exit__(None, None, None)
+            no_sync_context = None
+
+    disable_grad_sync()
 
     # Compute number of warmup microbatches.
-    num_warmup_microbatches = \
-        (parallel_state.get_pipeline_model_parallel_world_size() -
-         parallel_state.get_pipeline_model_parallel_rank() - 1)
-    num_warmup_microbatches = min(
-        num_warmup_microbatches,
-        num_microbatches)
-    num_microbatches_remaining = \
-        num_microbatches - num_warmup_microbatches
+    num_warmup_microbatches = (
+        parallel_state.get_pipeline_model_parallel_world_size()
+        - parallel_state.get_pipeline_model_parallel_rank()
+        - 1
+    )
+    num_warmup_microbatches = min(num_warmup_microbatches, num_microbatches)
+    num_microbatches_remaining = num_microbatches - num_warmup_microbatches
+
+    # Checkpoint the activations of partial Transformer layers in a number of micro-batches
+    # within the maximum outstanding micro-batch backpropagations.
+    # Micro-batches with the ids less than 'num_microbatches_with_partial_activation_checkpoints'
+    # checkpoint partial Transformer layers (or skip checkpointing) and
+    # the rest of micro-batches within a window of micro-batches checkpoint
+    # all Transformer layers. The window of micro-batches is set by the maximum
+    # outstanding backpropagations and becomes smaller at later pipeline stages.
+    # Please refer the appendix C in https://arxiv.org/pdf/2205.05198.pdf
+    max_outstanding_backprops = None
+    if config.num_microbatches_with_partial_activation_checkpoints is not None:
+        max_outstanding_backprops = num_warmup_microbatches + 1
 
     model_type = get_model_type(model)
 
     rank = parallel_state.get_pipeline_model_parallel_rank()
-    recv_tensor_shapes = get_tensor_shapes(rank=rank-1,
-                                           model_type=model_type,
-                                           tensor_shape=tensor_shape,
-                                           decoder_seq_length=decoder_seq_length,
-                                           sequence_parallel=sequence_parallel)
-    send_tensor_shapes = get_tensor_shapes(rank=rank,
-                                           model_type=model_type,
-                                           tensor_shape=tensor_shape,
-                                           decoder_seq_length=decoder_seq_length,
-                                           sequence_parallel=sequence_parallel)
+    recv_tensor_shapes = get_tensor_shapes(
+        rank=rank - 1,
+        model_type=model_type,
+        seq_length=seq_length,
+        micro_batch_size=micro_batch_size,
+        decoder_seq_length=decoder_seq_length,
+        config=config,
+    )
+    send_tensor_shapes = get_tensor_shapes(
+        rank=rank,
+        model_type=model_type,
+        seq_length=seq_length,
+        micro_batch_size=micro_batch_size,
+        decoder_seq_length=decoder_seq_length,
+        config=config,
+    )
 
     # Input, output tensors only need to be saved when doing backward passes
     input_tensors = None
@@ -782,77 +1130,125 @@ def forward_backward_pipelining_without_interleaving(*,
 
     # Run warmup forward passes.
     for i in range(num_warmup_microbatches):
-        input_tensor = recv_forward(recv_tensor_shapes, dtype, timers=timers)
-        output_tensor = forward_step(forward_step_func, data_iterator, model, num_microbatches,
-                                     input_tensor, forward_data_store,
-                                     timers, collect_non_loss_data, enable_autocast)
-        send_forward(output_tensor, send_tensor_shapes, timers=timers)
+        # Decide to checkpoint all layers' activations of the current micro-batch
+        if max_outstanding_backprops is not None:
+            checkpoint_activations_microbatch = (
+                i % max_outstanding_backprops
+                >= config.num_microbatches_with_partial_activation_checkpoints
+            )
+        else:
+            checkpoint_activations_microbatch = None
+
+        input_tensor = recv_forward(recv_tensor_shapes, config)
+        output_tensor = forward_step(
+            forward_step_func,
+            data_iterator,
+            model,
+            num_microbatches,
+            input_tensor,
+            forward_data_store,
+            config,
+            collect_non_loss_data,
+            checkpoint_activations_microbatch,
+        )
+        send_forward(output_tensor, send_tensor_shapes, config)
 
         if not forward_only:
             input_tensors.append(input_tensor)
             output_tensors.append(output_tensor)
-            deallocate_output_tensor(output_tensor[0])
+            deallocate_output_tensor(output_tensor[0], config.deallocate_pipeline_outputs)
 
     # Before running 1F1B, need to receive first forward tensor.
     # If all microbatches are run in warmup / cooldown phase, then no need to
     # receive this tensor here.
     if num_microbatches_remaining > 0:
-        input_tensor = recv_forward(recv_tensor_shapes, dtype, timers=timers)
+        input_tensor = recv_forward(recv_tensor_shapes, config)
 
     # Run 1F1B in steady state.
     for i in range(num_microbatches_remaining):
-        last_iteration = (i == (num_microbatches_remaining - 1))
+        last_iteration = i == (num_microbatches_remaining - 1)
 
-        output_tensor = forward_step(forward_step_func, data_iterator, model, num_microbatches,
-                                     input_tensor, forward_data_store,
-                                     timers, collect_non_loss_data, enable_autocast)
+        # Decide to checkpoint all layers' activations of the current micro-batch
+        if max_outstanding_backprops is not None:
+            checkpoint_activations_microbatch = (
+                (i + num_warmup_microbatches) % max_outstanding_backprops
+            ) >= config.num_microbatches_with_partial_activation_checkpoints
+        else:
+            checkpoint_activations_microbatch = None
+
+        output_tensor = forward_step(
+            forward_step_func,
+            data_iterator,
+            model,
+            num_microbatches,
+            input_tensor,
+            forward_data_store,
+            config,
+            collect_non_loss_data,
+            checkpoint_activations_microbatch,
+        )
 
         if forward_only:
-            send_forward(output_tensor, send_tensor_shapes, timers=timers)
+            send_forward(output_tensor, send_tensor_shapes, config)
 
             if not last_iteration:
-                input_tensor = recv_forward(recv_tensor_shapes, dtype, timers=timers)
+                input_tensor = recv_forward(recv_tensor_shapes, config)
 
         else:
-            output_tensor_grad = \
-                send_forward_recv_backward(output_tensor,
-                                           send_tensor_shapes, dtype,
-                                           timers=timers)
+            output_tensor_grad = send_forward_recv_backward(
+                output_tensor, send_tensor_shapes, config
+            )
 
             # Add input_tensor and output_tensor to end of list.
             input_tensors.append(input_tensor)
             output_tensors.append(output_tensor)
-            deallocate_output_tensor(output_tensor[0])
+            deallocate_output_tensor(output_tensor[0], config.deallocate_pipeline_outputs)
 
             # Pop input_tensor and output_tensor from the start of the list for
             # the backward pass.
             input_tensor = input_tensors.pop(0)
             output_tensor = output_tensors.pop(0)
 
-            input_tensor_grad = \
-                backward_step(grad_scaler, input_tensor, output_tensor,
-                              output_tensor_grad, model_type, timers)
+            input_tensor_grad = backward_step(
+                input_tensor, output_tensor, output_tensor_grad, model_type, config
+            )
 
             if last_iteration:
                 input_tensor = None
-                send_backward(input_tensor_grad, recv_tensor_shapes, timers=timers)
+                send_backward(input_tensor_grad, recv_tensor_shapes, config)
             else:
-                input_tensor = \
-                    send_backward_recv_forward(
-                        input_tensor_grad, recv_tensor_shapes, dtype, timers=timers)
+                input_tensor = send_backward_recv_forward(
+                    input_tensor_grad, recv_tensor_shapes, config
+                )
 
     # Run cooldown backward passes.
     if not forward_only:
         for i in range(num_warmup_microbatches):
+
+            # Enable async grad reduction in the last backward pass
+            # Note: If grad sync function is provided, only enable
+            # async grad reduction in first pipeline stage. Other
+            # pipeline stages do grad reduction during pipeline
+            # bubble.
+            if i == num_warmup_microbatches - 1:
+                if config.grad_sync_func is None or rank == 0:
+                    enable_grad_sync()
+
             input_tensor = input_tensors.pop(0)
             output_tensor = output_tensors.pop(0)
 
-            output_tensor_grad = recv_backward(send_tensor_shapes, dtype, timers=timers)
+            output_tensor_grad = recv_backward(send_tensor_shapes, config)
+
+            input_tensor_grad = backward_step(
+                input_tensor, output_tensor, output_tensor_grad, model_type, config
+            )
 
-            input_tensor_grad = \
-                backward_step(grad_scaler, input_tensor, output_tensor,
-                              output_tensor_grad, model_type, timers)
+            send_backward(input_tensor_grad, recv_tensor_shapes, config)
 
-            send_backward(input_tensor_grad, recv_tensor_shapes, timers=timers)
+    # Launch any remaining grad reductions
+    if no_sync_context is not None:
+        enable_grad_sync()
+        if config.grad_sync_func is not None:
+            config.grad_sync_func(model.parameters())
 
     return forward_data_store

megatron/core/requirements.txt

+torch
\ No newline at end of file

megatron/core/tensor_parallel/__init__.py

 from .cross_entropy import vocab_parallel_cross_entropy
 from .data import broadcast_data
-
 from .layers import (
     ColumnParallelLinear,
     RowParallelLinear,
     VocabParallelEmbedding,
-    set_tensor_model_parallel_attributes,
-    set_defaults_if_not_set_tensor_model_parallel_attributes,
     copy_tensor_model_parallel_attributes,
+    linear_with_grad_accumulation_and_async_allreduce,
     param_is_not_tensor_parallel_duplicate,
-    linear_with_grad_accumulation_and_async_allreduce
-
+    set_defaults_if_not_set_tensor_model_parallel_attributes,
+    set_tensor_model_parallel_attributes,
 )
-
 from .mappings import (
     copy_to_tensor_model_parallel_region,
-    gather_from_tensor_model_parallel_region,
     gather_from_sequence_parallel_region,
-    scatter_to_tensor_model_parallel_region,
+    gather_from_tensor_model_parallel_region,
     scatter_to_sequence_parallel_region,
+    scatter_to_tensor_model_parallel_region,
 )
-
-from .random import (
-    checkpoint,
-    get_cuda_rng_tracker,
-    model_parallel_cuda_manual_seed,
-)
-
+from .random import checkpoint, get_cuda_rng_tracker, model_parallel_cuda_manual_seed
 from .utils import (
+    gather_split_1d_tensor,
     split_tensor_along_last_dim,
     split_tensor_into_1d_equal_chunks,
-    gather_split_1d_tensor,
 )
 
 __all__ = [
@@ -38,7 +29,7 @@ __all__ = [
     "vocab_parallel_cross_entropy",
     # data.py
     "broadcast_data",
-    #layers.py
+    # layers.py
     "ColumnParallelLinear",
     "RowParallelLinear",
     "VocabParallelEmbedding",
@@ -51,7 +42,7 @@ __all__ = [
     "copy_to_tensor_model_parallel_region",
     "gather_from_tensor_model_parallel_region",
     "gather_from_sequence_parallel_region",
-#    "reduce_from_tensor_model_parallel_region",
+    #    "reduce_from_tensor_model_parallel_region",
     "scatter_to_tensor_model_parallel_region",
     "scatter_to_sequence_parallel_region",
     # random.py

megatron/core/tensor_parallel/cross_entropy.py

@@ -5,22 +5,21 @@ import torch
 from megatron.core.parallel_state import (
     get_tensor_model_parallel_group,
     get_tensor_model_parallel_rank,
-    get_tensor_model_parallel_world_size
+    get_tensor_model_parallel_world_size,
 )
 
 from .utils import VocabUtility
 
 
 class _VocabParallelCrossEntropy(torch.autograd.Function):
-
     @staticmethod
     def forward(ctx, vocab_parallel_logits, target, label_smoothing=0.0):
 
         # Maximum value along vocab dimension across all GPUs.
         logits_max = torch.max(vocab_parallel_logits, dim=-1)[0]
-        torch.distributed.all_reduce(logits_max,
-                                     op=torch.distributed.ReduceOp.MAX,
-                                     group=get_tensor_model_parallel_group())
+        torch.distributed.all_reduce(
+            logits_max, op=torch.distributed.ReduceOp.MAX, group=get_tensor_model_parallel_group()
+        )
         # Subtract the maximum value.
         vocab_parallel_logits = vocab_parallel_logits - logits_max.unsqueeze(dim=-1)
 
@@ -29,8 +28,7 @@ class _VocabParallelCrossEntropy(torch.autograd.Function):
         partition_vocab_size = vocab_parallel_logits.size()[-1]
         rank = get_tensor_model_parallel_rank()
         world_size = get_tensor_model_parallel_world_size()
-        vocab_start_index, vocab_end_index = get_vocab_range(
-            partition_vocab_size, rank, world_size)
+        vocab_start_index, vocab_end_index = get_vocab_range(partition_vocab_size, rank, world_size)
 
         # Create a mask of valid vocab ids (1 means it needs to be masked).
         target_mask = (target < vocab_start_index) | (target >= vocab_end_index)
@@ -42,24 +40,27 @@ class _VocabParallelCrossEntropy(torch.autograd.Function):
         # [*, partition-vocab-size] and target to a 1-D tensor of size [*].
         logits_2d = vocab_parallel_logits.view(-1, partition_vocab_size)
         masked_target_1d = masked_target.view(-1)
-        arange_1d = torch.arange(start=0, end=logits_2d.size()[0],
-                                 device=logits_2d.device)
+        arange_1d = torch.arange(start=0, end=logits_2d.size()[0], device=logits_2d.device)
         predicted_logits_1d = logits_2d[arange_1d, masked_target_1d]
         predicted_logits_1d = predicted_logits_1d.clone().contiguous()
         predicted_logits = predicted_logits_1d.view_as(target)
         predicted_logits[target_mask] = 0.0
         # All reduce is needed to get the chunks from other GPUs.
-        torch.distributed.all_reduce(predicted_logits,
-                                     op=torch.distributed.ReduceOp.SUM,
-                                     group=get_tensor_model_parallel_group())
+        torch.distributed.all_reduce(
+            predicted_logits,
+            op=torch.distributed.ReduceOp.SUM,
+            group=get_tensor_model_parallel_group(),
+        )
 
         # Sum of exponential of logits along vocab dimension across all GPUs.
         exp_logits = vocab_parallel_logits
         torch.exp(vocab_parallel_logits, out=exp_logits)
         sum_exp_logits = exp_logits.sum(dim=-1)
-        torch.distributed.all_reduce(sum_exp_logits,
-                                     op=torch.distributed.ReduceOp.SUM,
-                                     group=get_tensor_model_parallel_group())
+        torch.distributed.all_reduce(
+            sum_exp_logits,
+            op=torch.distributed.ReduceOp.SUM,
+            group=get_tensor_model_parallel_group(),
+        )
 
         # Loss = log(sum(exp(logits))) - predicted-logit.
         loss = torch.log(sum_exp_logits) - predicted_logits
@@ -87,7 +88,6 @@ class _VocabParallelCrossEntropy(torch.autograd.Function):
             loss = (1.0 - smoothing) * loss - smoothing * mean_log_probs
 
         ctx.label_smoothing, ctx.vocab_size = label_smoothing, vocab_size
-        ctx.save_for_backward(exp_logits, target_mask, masked_target_1d)
 
         # Store softmax, target-mask and masked-target for backward pass.
         ctx.save_for_backward(exp_logits, target_mask, masked_target_1d)
@@ -108,8 +108,7 @@ class _VocabParallelCrossEntropy(torch.autograd.Function):
         grad_2d = grad_input.view(-1, partition_vocab_size)
 
         # Add the gradient from matching classes.
-        arange_1d = torch.arange(start=0, end=grad_2d.size()[0],
-                                 device=grad_2d.device)
+        arange_1d = torch.arange(start=0, end=grad_2d.size()[0], device=grad_2d.device)
 
         softmax_update = 1.0 - target_mask.view(-1).float()
 

megatron/core/tensor_parallel/data.py

@@ -8,15 +8,16 @@ from megatron.core.parallel_state import (
     get_tensor_model_parallel_src_rank,
 )
 
-
 _MAX_DATA_DIM = 5
 
 
 def _check_data_types(keys, data, target_dtype):
     """Check that all the keys have the same target data type."""
     for key in keys:
-        assert data[key].dtype == target_dtype, '{} has data type {} which '\
+        assert data[key].dtype == target_dtype, (
+            '{} has data type {} which '
             'is different than {}'.format(key, data[key].dtype, target_dtype)
+        )
 
 
 def _build_key_size_numel_dictionaries(keys, data):
@@ -36,8 +37,9 @@ def _build_key_size_numel_dictionaries(keys, data):
 
     # Move to GPU and broadcast.
     sizes_cuda = torch.cuda.LongTensor(sizes)
-    torch.distributed.broadcast(sizes_cuda, get_tensor_model_parallel_src_rank(),
-                                group=get_tensor_model_parallel_group())
+    torch.distributed.broadcast(
+        sizes_cuda, get_tensor_model_parallel_src_rank(), group=get_tensor_model_parallel_group()
+    )
 
     # Move back to cpu and unpack.
     sizes_cpu = sizes_cuda.cpu()
@@ -74,24 +76,21 @@ def broadcast_data(keys, data, datatype):
     """
     # Build (key, size) and (key, number of elements) dictionaries along
     # with the total number of elements on all ranks.
-    key_size, key_numel, total_numel = _build_key_size_numel_dictionaries(keys,
-                                                                          data)
+    key_size, key_numel, total_numel = _build_key_size_numel_dictionaries(keys, data)
 
     # Pack on rank zero.
     if get_tensor_model_parallel_rank() == 0:
         # Check that all keys have the same data type.
         _check_data_types(keys, data, datatype)
         # Flatten the data associated with the keys
-        flatten_data = torch.cat(
-            [data[key].contiguous().view(-1) for key in keys], dim=0).cuda()
+        flatten_data = torch.cat([data[key].contiguous().view(-1) for key in keys], dim=0).cuda()
     else:
-        flatten_data = torch.empty(total_numel,
-                                   device=torch.cuda.current_device(),
-                                   dtype=datatype)
+        flatten_data = torch.empty(total_numel, device=torch.cuda.current_device(), dtype=datatype)
 
     # Broadcast
-    torch.distributed.broadcast(flatten_data, get_tensor_model_parallel_src_rank(),
-                                group=get_tensor_model_parallel_group())
+    torch.distributed.broadcast(
+        flatten_data, get_tensor_model_parallel_src_rank(), group=get_tensor_model_parallel_group()
+    )
 
     # Unpack
     output = {}

megatron/core/tensor_parallel/layers.py

@@ -5,37 +5,33 @@
 
 import math
 import os
-from typing import Optional
 import warnings
+from typing import Callable, Optional
 
 import torch
 import torch.nn.functional as F
 import torch.nn.init as init
+from torch.cuda.amp import custom_bwd, custom_fwd
 from torch.nn.parameter import Parameter
 
-from torch.cuda.amp import custom_fwd, custom_bwd
-
+from megatron.core.model_parallel_config import ModelParallelConfig
 from megatron.core.parallel_state import (
+    get_global_memory_buffer,
+    get_tensor_model_parallel_group,
     get_tensor_model_parallel_rank,
     get_tensor_model_parallel_world_size,
-    get_tensor_model_parallel_group,
-    get_global_memory_buffer,
 )
+
 from .mappings import (
     copy_to_tensor_model_parallel_region,
-    gather_from_tensor_model_parallel_region,
     gather_from_sequence_parallel_region,
+    gather_from_tensor_model_parallel_region,
     reduce_from_tensor_model_parallel_region,
-    scatter_to_tensor_model_parallel_region,
     reduce_scatter_to_sequence_parallel_region,
+    scatter_to_tensor_model_parallel_region,
 )
-
 from .random import get_cuda_rng_tracker
-from .utils import (
-    divide,
-    split_tensor_along_last_dim,
-    VocabUtility,
-)
+from .utils import VocabUtility, divide, split_tensor_along_last_dim
 
 _grad_accum_fusion_available = True
 try:
@@ -43,14 +39,17 @@ try:
 except ImportError:
     _grad_accum_fusion_available = False
 
-_MODEL_PARALLEL_ATTRIBUTE_DEFAULTS = {'tensor_model_parallel': False,
-                                      'partition_dim': -1,
-                                      'partition_stride': 1}
+_MODEL_PARALLEL_ATTRIBUTE_DEFAULTS = {
+    'tensor_model_parallel': False,
+    'partition_dim': -1,
+    'partition_stride': 1,
+}
+
 
 def param_is_not_tensor_parallel_duplicate(param):
-    return (hasattr(param, 'tensor_model_parallel') and
-            param.tensor_model_parallel) or (
-                get_tensor_model_parallel_rank() == 0)
+    return (hasattr(param, 'tensor_model_parallel') and param.tensor_model_parallel) or (
+        get_tensor_model_parallel_rank() == 0
+    )
 
 
 def set_tensor_model_parallel_attributes(tensor, is_parallel, dim, stride):
@@ -67,6 +66,7 @@ def set_defaults_if_not_set_tensor_model_parallel_attributes(tensor):
     def maybe_set(attribute, value):
         if not hasattr(tensor, attribute):
             setattr(tensor, attribute, value)
+
     for attribute in _MODEL_PARALLEL_ATTRIBUTE_DEFAULTS:
         maybe_set(attribute, _MODEL_PARALLEL_ATTRIBUTE_DEFAULTS[attribute])
 
@@ -74,51 +74,52 @@ def set_defaults_if_not_set_tensor_model_parallel_attributes(tensor):
 def copy_tensor_model_parallel_attributes(destination_tensor, source_tensor):
     def maybe_copy(attribute):
         if hasattr(source_tensor, attribute):
-            setattr(destination_tensor, attribute,
-                    getattr(source_tensor, attribute))
+            setattr(destination_tensor, attribute, getattr(source_tensor, attribute))
+
     for attribute in _MODEL_PARALLEL_ATTRIBUTE_DEFAULTS:
         maybe_copy(attribute)
 
 
-def _initialize_affine_weight_gpu(weight, init_method,
-                                  partition_dim, stride=1):
+def _initialize_affine_weight_gpu(weight, init_method, partition_dim, stride=1):
     """Initialize affine weight for model parallel on GPU."""
 
-    set_tensor_model_parallel_attributes(tensor=weight,
-                                         is_parallel=True,
-                                         dim=partition_dim,
-                                         stride=stride)
+    set_tensor_model_parallel_attributes(
+        tensor=weight, is_parallel=True, dim=partition_dim, stride=stride
+    )
 
     with get_cuda_rng_tracker().fork():
         init_method(weight)
 
 
-def _initialize_affine_weight_cpu(weight, output_size, input_size,
-                                  per_partition_size, partition_dim,
-                                  init_method, stride=1,
-                                  return_master_weight=False,
-                                  *, params_dtype=torch.float32):
+def _initialize_affine_weight_cpu(
+    weight,
+    output_size,
+    input_size,
+    per_partition_size,
+    partition_dim,
+    init_method,
+    stride=1,
+    return_master_weight=False,
+    *,
+    params_dtype=torch.float32,
+):
     """Initialize affine weight for model parallel.
 
     Build the master weight on all processes and scatter
     the relevant chunk."""
 
-    set_tensor_model_parallel_attributes(tensor=weight,
-                                         is_parallel=True,
-                                         dim=partition_dim,
-                                         stride=stride)
+    set_tensor_model_parallel_attributes(
+        tensor=weight, is_parallel=True, dim=partition_dim, stride=stride
+    )
 
     # Initialize master weight
-    master_weight = torch.empty(output_size, input_size,
-                                dtype=torch.float,
-                                requires_grad=False)
+    master_weight = torch.empty(output_size, input_size, dtype=torch.float, requires_grad=False)
     init_method(master_weight)
     master_weight = master_weight.to(dtype=params_dtype)
 
     # Split and copy
     per_partition_per_stride_size = divide(per_partition_size, stride)
-    weight_list = torch.split(master_weight, per_partition_per_stride_size,
-                              dim=partition_dim)
+    weight_list = torch.split(master_weight, per_partition_per_stride_size, dim=partition_dim)
     rank = get_tensor_model_parallel_rank()
     world_size = get_tensor_model_parallel_world_size()
     my_weight_list = weight_list[rank::world_size]
@@ -140,17 +141,17 @@ class VocabParallelEmbedding(torch.nn.Module):
         embedding_dim: size of hidden state.
 
     Keyword Arguments:
-        init_method: method to initialize weights.
-        params_dtype
-        use_cpu_initialization
-        perform_initialization
+        config: A megatron.core.ModelParallelConfig object
     """
 
-    def __init__(self, num_embeddings: int, embedding_dim: int, *,
-                 init_method=init.xavier_normal_,
-                 params_dtype: torch.dtype=torch.float32,
-                 use_cpu_initialization: bool=False,
-                 perform_initialization: bool=True):
+    def __init__(
+        self,
+        num_embeddings: int,
+        embedding_dim: int,
+        *,
+        init_method: Callable,
+        config: ModelParallelConfig,
+    ):
         super(VocabParallelEmbedding, self).__init__()
         # Keep the input dimensions.
         self.num_embeddings = num_embeddings
@@ -158,52 +159,68 @@ class VocabParallelEmbedding(torch.nn.Module):
         # Set the detauls for compatibility.
         self.padding_idx = None
         self.max_norm = None
-        self.norm_type = 2.
+        self.norm_type = 2.0
         self.scale_grad_by_freq = False
         self.sparse = False
         self._weight = None
         self.tensor_model_parallel_size = get_tensor_model_parallel_world_size()
         # Divide the weight matrix along the vocaburaly dimension.
-        self.vocab_start_index, self.vocab_end_index = \
-            VocabUtility.vocab_range_from_global_vocab_size(
-                self.num_embeddings, get_tensor_model_parallel_rank(),
-                self.tensor_model_parallel_size)
-        self.num_embeddings_per_partition = self.vocab_end_index - \
-            self.vocab_start_index
+        (
+            self.vocab_start_index,
+            self.vocab_end_index,
+        ) = VocabUtility.vocab_range_from_global_vocab_size(
+            self.num_embeddings, get_tensor_model_parallel_rank(), self.tensor_model_parallel_size
+        )
+        self.num_embeddings_per_partition = self.vocab_end_index - self.vocab_start_index
 
         # Allocate weights and initialize.
-        if use_cpu_initialization:
-            self.weight = Parameter(torch.empty(
-                self.num_embeddings_per_partition, self.embedding_dim,
-                dtype=params_dtype))
-            if perform_initialization:
+        if config.use_cpu_initialization:
+            self.weight = Parameter(
+                torch.empty(
+                    self.num_embeddings_per_partition, self.embedding_dim, dtype=config.params_dtype
+                )
+            )
+            if config.perform_initialization:
                 _initialize_affine_weight_cpu(
-                    self.weight, self.num_embeddings, self.embedding_dim,
-                    self.num_embeddings_per_partition, 0, init_method,
-                    params_dtype=params_dtype)
+                    self.weight,
+                    self.num_embeddings,
+                    self.embedding_dim,
+                    self.num_embeddings_per_partition,
+                    0,
+                    init_method,
+                    params_dtype=config.params_dtype,
+                )
         else:
-            self.weight = Parameter(torch.empty(
-                self.num_embeddings_per_partition, self.embedding_dim,
-                device=torch.cuda.current_device(), dtype=params_dtype))
-            if perform_initialization:
-                _initialize_affine_weight_gpu(self.weight, init_method,
-                                              partition_dim=0, stride=1)
+            self.weight = Parameter(
+                torch.empty(
+                    self.num_embeddings_per_partition,
+                    self.embedding_dim,
+                    device=torch.cuda.current_device(),
+                    dtype=config.params_dtype,
+                )
+            )
+            if config.perform_initialization:
+                _initialize_affine_weight_gpu(self.weight, init_method, partition_dim=0, stride=1)
 
     def forward(self, input_):
         if self.tensor_model_parallel_size > 1:
             # Build the mask.
-            input_mask = (input_ < self.vocab_start_index) | \
-                         (input_ >= self.vocab_end_index)
+            input_mask = (input_ < self.vocab_start_index) | (input_ >= self.vocab_end_index)
             # Mask the input.
             masked_input = input_.clone() - self.vocab_start_index
             masked_input[input_mask] = 0
         else:
             masked_input = input_
             # Get the embeddings.
-        output_parallel = F.embedding(masked_input, self.weight,
-                                      self.padding_idx, self.max_norm,
-                                      self.norm_type, self.scale_grad_by_freq,
-                                      self.sparse)
+        output_parallel = F.embedding(
+            masked_input,
+            self.weight,
+            self.padding_idx,
+            self.max_norm,
+            self.norm_type,
+            self.scale_grad_by_freq,
+            self.sparse,
+        )
         # Mask the output embedding.
         if self.tensor_model_parallel_size > 1:
             output_parallel[input_mask, :] = 0.0
@@ -212,13 +229,97 @@ class VocabParallelEmbedding(torch.nn.Module):
         return output
 
 
+class LinearWithFrozenWeight(torch.autograd.Function):
+    """Linear operator that does not calculate gradient for weight.
+    This op and LinearWithGradAccumulationAndAsyncCommunication performs 
+    mathematically-identical forward and DGRAD. 
+    
+    Conceptually this op is the same as torch.nn.functional.linear with
+    weight.requires_grad==False, but in experiments they are not identical 
+    mathematically. """
+
+    @staticmethod
+    @custom_fwd
+    def forward(
+        ctx, input, weight, bias,
+    ):
+        ctx.save_for_backward(weight)
+        output = torch.matmul(input, weight.t())
+        if bias is not None:
+            output = output + bias
+        return output
+
+    @staticmethod
+    @custom_bwd
+    def backward(ctx, grad_output):
+        (weight,) = ctx.saved_tensors
+        grad_input = grad_output.matmul(weight)
+        return grad_input, None, None
+
+
+def linear_with_frozen_weight(
+    input: torch.Tensor,
+    weight: torch.Tensor,
+    bias: Optional[torch.Tensor],
+    gradient_accumulation_fusion: bool,
+    async_grad_allreduce: bool,
+    sequence_parallel: bool,
+) -> torch.Tensor:
+    """Linear layer execution with weight.requires_grad == False.
+
+    This function handles linear layers with weight frozen (untrainable). 
+    In the forward, it only saves weight and does not save input activations.
+    In the backward, it does not perform weight gradient calculation, or 
+    weight gradient allreduce. 
+
+    Arguments:
+
+    input (torch.Tensor required): input like torch.nn.functional.linear
+
+    weight (torch.Tensor required): weight like torch.nn.functional.linear
+
+    bias (torch.Tensor optional): bias like torch.nn.functional.linear
+
+    gradient_accumulation_fusion (bool required): dummy argument, used to 
+    keep the API unified between all forward implementation functions.
+
+    async_grad_allreduce (bool required): dummy argument, used to 
+    keep the API unified between all forward implementation functions.
+
+    sequence_parallel (bool required): Indicates that sequence
+        parallelism is used and thus in the forward pass the input is
+        all gathered, and the backward pass the input gradients are
+        reduce scattered.
+    """
+
+    if sequence_parallel:
+        input = gather_from_sequence_parallel_region(input, tensor_parallel_output_grad=True)
+    else:
+        input = input
+
+    args = [
+        input,
+        weight,
+        bias,
+    ]
+
+    return LinearWithFrozenWeight.apply(*args)
+
+
 class LinearWithGradAccumulationAndAsyncCommunication(torch.autograd.Function):
     """See linear_with_grad_accumulation_and_async_allreduce"""
 
     @staticmethod
     @custom_fwd
-    def forward(ctx, input, weight, bias, gradient_accumulation_fusion,
-                async_grad_allreduce, sequence_parallel):
+    def forward(
+        ctx,
+        input,
+        weight,
+        bias,
+        gradient_accumulation_fusion,
+        async_grad_allreduce,
+        sequence_parallel,
+    ):
         ctx.save_for_backward(input, weight)
         ctx.use_bias = bias is not None
         ctx.gradient_accumulation_fusion = gradient_accumulation_fusion
@@ -230,12 +331,10 @@ class LinearWithGradAccumulationAndAsyncCommunication(torch.autograd.Function):
             dim_size = list(input.size())
             dim_size[0] = dim_size[0] * world_size
 
-            all_gather_buffer = \
-                get_global_memory_buffer().get_tensor(dim_size, input.dtype, "mpu")
+            all_gather_buffer = get_global_memory_buffer().get_tensor(dim_size, input.dtype, "mpu")
             torch.distributed._all_gather_base(
-                all_gather_buffer,
-                input,
-                group=get_tensor_model_parallel_group())
+                all_gather_buffer, input, group=get_tensor_model_parallel_group()
+            )
             total_input = all_gather_buffer
         else:
             total_input = input
@@ -256,12 +355,10 @@ class LinearWithGradAccumulationAndAsyncCommunication(torch.autograd.Function):
             dim_size = list(input.size())
             dim_size[0] = dim_size[0] * world_size
 
-            all_gather_buffer = \
-                get_global_memory_buffer().get_tensor(dim_size, input.dtype, "mpu")
+            all_gather_buffer = get_global_memory_buffer().get_tensor(dim_size, input.dtype, "mpu")
             handle = torch.distributed._all_gather_base(
-                all_gather_buffer,
-                input,
-                group=get_tensor_model_parallel_group(), async_op=True)
+                all_gather_buffer, input, group=get_tensor_model_parallel_group(), async_op=True
+            )
 
             # Here we rely on CUDA_DEVICE_MAX_CONNECTIONS=1 to ensure that the
             # gather is scheduled before the input gradient computation
@@ -273,43 +370,49 @@ class LinearWithGradAccumulationAndAsyncCommunication(torch.autograd.Function):
         if ctx.sequence_parallel:
             handle.wait()
 
-        # Doing gather + slicing during the NeMo forward pass can make this tensor 
-        # not be contiguous. PyTorch only checks if the tensor is contiguous, and only 
-        # clones it if it's not contiguous: 
+        # Doing gather + slicing during the NeMo forward pass can make this tensor
+        # not be contiguous. PyTorch only checks if the tensor is contiguous, and only
+        # clones it if it's not contiguous:
         # https://github.com/pytorch/pytorch/blob/c47cf9bc7f9e02f649ab4ed53fe4d35732c92ab6/torch/_refs/__init__.py#L2761
         grad_output = grad_output.contiguous()
         # Convert the tensor shapes to 2D for execution compatibility
-        grad_output = grad_output.view(grad_output.shape[0] * grad_output.shape[1],
-                                       grad_output.shape[2])
-        total_input = total_input.view(total_input.shape[0] * total_input.shape[1],
-				       total_input.shape[2])
+        grad_output = grad_output.view(
+            grad_output.shape[0] * grad_output.shape[1], grad_output.shape[2]
+        )
+        total_input = total_input.view(
+            total_input.shape[0] * total_input.shape[1], total_input.shape[2]
+        )
 
         if ctx.async_grad_allreduce:
             # Asynchronous all-reduce
             handle = torch.distributed.all_reduce(
-                    grad_input, group=get_tensor_model_parallel_group(), async_op=True)
+                grad_input, group=get_tensor_model_parallel_group(), async_op=True
+            )
             # Here we rely on CUDA_DEVICE_MAX_CONNECTIONS=1 to ensure that the
             # all-reduce is scheduled before the weight gradient computation
 
         if ctx.sequence_parallel:
             assert not ctx.async_grad_allreduce
             dim_size = list(input.size())
-            sub_grad_input = torch.empty(dim_size, dtype=input.dtype,
-                                         device=torch.cuda.current_device(),
-                                         requires_grad=False)
+            sub_grad_input = torch.empty(
+                dim_size, dtype=input.dtype, device=torch.cuda.current_device(), requires_grad=False
+            )
             # reduce_scatter
-            handle = torch.distributed._reduce_scatter_base(sub_grad_input, grad_input,
-                                                            group=get_tensor_model_parallel_group(),
-                                                            async_op=True)
+            handle = torch.distributed._reduce_scatter_base(
+                sub_grad_input, grad_input, group=get_tensor_model_parallel_group(), async_op=True
+            )
             # Here we rely on CUDA_DEVICE_MAX_CONNECTIONS=1 to ensure that the
             # reduce scatter is scheduled before the weight gradient computation
 
-
         if ctx.gradient_accumulation_fusion:
             if weight.main_grad.dtype == torch.float32:
-                fused_weight_gradient_mlp_cuda.wgrad_gemm_accum_fp32(total_input, grad_output, weight.main_grad)
-            elif weight.main_grad.dtype == torch.float16:
-                fused_weight_gradient_mlp_cuda.wgrad_gemm_accum_fp16(total_input, grad_output, weight.main_grad)
+                fused_weight_gradient_mlp_cuda.wgrad_gemm_accum_fp32(
+                    total_input, grad_output, weight.main_grad
+                )
+            elif weight.main_grad.dtype in (torch.float16, torch.bfloat16):
+                fused_weight_gradient_mlp_cuda.wgrad_gemm_accum_fp16(
+                    total_input, grad_output, weight.main_grad
+                )
             else:
                 raise RuntimeError("Unsupported gradient type for gradient accumulation fusion")
             grad_weight = None
@@ -326,13 +429,14 @@ class LinearWithGradAccumulationAndAsyncCommunication(torch.autograd.Function):
 
         return grad_input, grad_weight, grad_bias, None, None, None
 
+
 def linear_with_grad_accumulation_and_async_allreduce(
     input: torch.Tensor,
     weight: torch.Tensor,
     bias: Optional[torch.Tensor],
     gradient_accumulation_fusion: bool,
     async_grad_allreduce: bool,
-    sequence_parallel_enabled: bool,
+    sequence_parallel: bool,
 ) -> torch.Tensor:
     """Linear layer execution with asynchronous communication and
     gradient accumulation fusion in backprop.
@@ -378,10 +482,10 @@ def linear_with_grad_accumulation_and_async_allreduce(
 
     async_grad_allreduce (bool required): Do the allreduce of input
         gradients asyncronously with the computation of weight
-        gradients. If sequence_parallel_enabled is True, this must be
+        gradients. If sequence_parallel is True, this must be
         False, as no all reduce is performed.
 
-    sequence_parallel_enabled (bool required): Indicates that sequence
+    sequence_parallel (bool required): Indicates that sequence
         parallelism is used and thus in the forward pass the input is
         all gathered, and the backward pass the input gradients are
         reduce scattered.
@@ -392,29 +496,33 @@ def linear_with_grad_accumulation_and_async_allreduce(
         bias,
         gradient_accumulation_fusion,
         async_grad_allreduce,
-        sequence_parallel_enabled,
+        sequence_parallel,
     ]
 
     if not linear_with_grad_accumulation_and_async_allreduce.warned:
         if os.environ.get('CUDA_DEVICE_MAX_CONNECTIONS') != "1":
-            if sequence_parallel_enabled:
+            if sequence_parallel:
                 warnings.warn(
                     "When using sequence parallelism it is recommended to set the "
                     "environment variable CUDA_DEVICE_MAX_CONNECTIONS to 1 for "
-                    "maximum speedup")
+                    "maximum speedup"
+                )
                 linear_with_grad_accumulation_and_async_allreduce.warned = True
 
             if async_grad_allreduce:
                 warnings.warn(
                     "When using async grad allreduce it is recommended to set the "
                     "environment variable CUDA_DEVICE_MAX_CONNECTIONS to 1 for "
-                    "maximum speedup")
+                    "maximum speedup"
+                )
                 linear_with_grad_accumulation_and_async_allreduce.warned = True
 
     return LinearWithGradAccumulationAndAsyncCommunication.apply(*args)
 
+
 linear_with_grad_accumulation_and_async_allreduce.warned = False
 
+
 class ColumnParallelLinear(torch.nn.Module):
     """Linear layer with column parallelism.
 
@@ -436,28 +544,34 @@ class ColumnParallelLinear(torch.nn.Module):
         keep_master_weight_for_test: This was added for testing and should be
                                      set to False. It returns the master weights
                                      used for initialization.
-        skip_bias_add: This was added to enable performance optimations where bias
-                       can be fused with other elementwise operations. we skip
-                       adding bias but instead return it.
-        async_tensor_model_parallel_allreduce:
-        params_dtype:
-        use_cpu_initialization:
-        gradient_accumulation_fusion:
-        sequence_parallel_enabled:
+        skip_bias_add: If True, do not add the bias term, instead
+                       return it to be added by the caller. This
+                       enables performance optimations where bias can
+                       be fused with other elementwise operations.
+
+        skip_weight_param_allocation: If True, weight parameter is not allocated and must be passed
+                                      as a keyword argument `weight` during the forward pass. Note
+                                      that this does not affect bias, which will be allocated if
+                                      bias is True. Defaults to False.
+
+        config: ModelParallelConfig object
+
     """
 
-    def __init__(self, input_size, output_size, *,
-                 bias=True, gather_output=True,
-                 init_method=init.xavier_normal_, stride=1,
-                 keep_master_weight_for_test=False,
-                 skip_bias_add=False,
-                 async_tensor_model_parallel_allreduce=True,
-                 params_dtype=torch.float32,
-                 use_cpu_initialization=False,
-                 perform_initialization=True,
-                 gradient_accumulation_fusion=False,
-                 sequence_parallel_enabled: bool = False,
-                 ):
+    def __init__(
+        self,
+        input_size,
+        output_size,
+        *,
+        config: ModelParallelConfig,
+        init_method: Callable,
+        bias=True,
+        gather_output=False,
+        stride=1,
+        keep_master_weight_for_test=False,
+        skip_bias_add=False,
+        skip_weight_param_allocation: bool = False,
+    ):
         super(ColumnParallelLinear, self).__init__()
 
         # Keep input parameters
@@ -468,105 +582,151 @@ class ColumnParallelLinear(torch.nn.Module):
         world_size = get_tensor_model_parallel_world_size()
         self.output_size_per_partition = divide(output_size, world_size)
         self.skip_bias_add = skip_bias_add
+        self.config = config
 
         # Parameters.
         # Note: torch.nn.functional.linear performs XA^T + b and as a result
         # we allocate the transpose.
         # Initialize weight.
-        if use_cpu_initialization:
-            self.weight = Parameter(torch.empty(self.output_size_per_partition,
-                                                self.input_size,
-                                                dtype=params_dtype))
-            if perform_initialization:
-                self.master_weight = _initialize_affine_weight_cpu(
-                    self.weight, self.output_size, self.input_size,
-                    self.output_size_per_partition, 0, init_method,
-                    stride=stride, return_master_weight=keep_master_weight_for_test)
+        if not skip_weight_param_allocation:
+            if config.use_cpu_initialization:
+                self.weight = Parameter(
+                    torch.empty(
+                        self.output_size_per_partition, self.input_size, dtype=config.params_dtype
+                    )
+                )
+                if config.perform_initialization:
+                    self.master_weight = _initialize_affine_weight_cpu(
+                        self.weight,
+                        self.output_size,
+                        self.input_size,
+                        self.output_size_per_partition,
+                        0,
+                        init_method,
+                        stride=stride,
+                        return_master_weight=keep_master_weight_for_test,
+                    )
+            else:
+                self.weight = Parameter(
+                    torch.empty(
+                        self.output_size_per_partition,
+                        self.input_size,
+                        device=torch.cuda.current_device(),
+                        dtype=config.params_dtype,
+                    )
+                )
+                if config.perform_initialization:
+                    _initialize_affine_weight_gpu(
+                        self.weight, init_method, partition_dim=0, stride=stride
+                    )
         else:
-            self.weight = Parameter(torch.empty(
-                self.output_size_per_partition, self.input_size,
-                device=torch.cuda.current_device(), dtype=params_dtype))
-            if perform_initialization:
-                _initialize_affine_weight_gpu(self.weight, init_method,
-                                              partition_dim=0, stride=stride)
+            self.weight = None
 
         if bias:
-            if use_cpu_initialization:
-                self.bias = Parameter(torch.empty(
-                    self.output_size_per_partition, dtype=params_dtype))
+            if config.use_cpu_initialization:
+                self.bias = Parameter(
+                    torch.empty(self.output_size_per_partition, dtype=config.params_dtype)
+                )
             else:
-                self.bias = Parameter(torch.empty(
-                    self.output_size_per_partition,
-                    device=torch.cuda.current_device(),
-                    dtype=params_dtype))
+                self.bias = Parameter(
+                    torch.empty(
+                        self.output_size_per_partition,
+                        device=torch.cuda.current_device(),
+                        dtype=config.params_dtype,
+                    )
+                )
             set_tensor_model_parallel_attributes(self.bias, True, 0, stride)
-            # Always initialize bias to zero.
-            with torch.no_grad():
-                self.bias.zero_()
+            if config.perform_initialization:
+                # Always initialize bias to zero.
+                with torch.no_grad():
+                    self.bias.zero_()
         else:
             self.register_parameter('bias', None)
 
         self.async_tensor_model_parallel_allreduce = (
-                async_tensor_model_parallel_allreduce and
-                world_size > 1)
-        if sequence_parallel_enabled:
-            if world_size <= 1:
-                warnings.warn(
-                    f"`sequence_parallel_enabled` is set to `True`, but tensor model parallel size is {world_size}. "
-                    f"Disabling sequence parallel."
-                )
-                sequence_parallel_enabled = False
-        self.sequence_parallel_enabled = sequence_parallel_enabled
+            config.async_tensor_model_parallel_allreduce and world_size > 1
+        )
 
-        if gradient_accumulation_fusion:
-            if not _grad_accum_fusion_available:
-                raise RuntimeError(
-                    "ColumnParallelLinear was called with gradient_accumulation_fusion set "
-                    "to True but the custom CUDA extension fused_weight_gradient_mlp_cuda "
-                    "module is not found. To use gradient_accumulation_fusion you must "
-                    "install APEX with --cpp_ext and --cuda_ext. For example: "
-                    "pip install --global-option=\"--cpp_ext\" --global-option=\"--cuda_ext .\" "
-                    "Note that the extension requires CUDA>=11. Otherwise, you must turn off "
-                    "gradient accumulation fusion."
-                )
-        self.gradient_accumulation_fusion = gradient_accumulation_fusion
+        self.sequence_parallel = config.sequence_parallel
+        if self.sequence_parallel and world_size <= 1:
+            warnings.warn(
+                f"`sequence_parallel` is set to `True`, but tensor model parallel size is {world_size}. "
+                f"Disabling sequence parallel."
+            )
+            self.sequence_parallel = False
+
+        if config.gradient_accumulation_fusion and not _grad_accum_fusion_available:
+            raise RuntimeError(
+                "ColumnParallelLinear was called with gradient_accumulation_fusion set "
+                "to True but the custom CUDA extension fused_weight_gradient_mlp_cuda "
+                "module is not found. To use gradient_accumulation_fusion you must "
+                "install APEX with --cpp_ext and --cuda_ext. For example: "
+                "pip install --global-option=\"--cpp_ext\" --global-option=\"--cuda_ext .\" "
+                "Note that the extension requires CUDA>=11. Otherwise, you must turn off "
+                "gradient accumulation fusion."
+            )
+        self.gradient_accumulation_fusion = config.gradient_accumulation_fusion
 
-        if self.async_tensor_model_parallel_allreduce and self.sequence_parallel_enabled:
+        if self.async_tensor_model_parallel_allreduce and self.sequence_parallel:
             raise RuntimeError(
-                "`async_tensor_model_parallel_allreduce` and `sequence_parallel_enabled` "
+                "`async_tensor_model_parallel_allreduce` and `sequence_parallel` "
                 "cannot be enabled at the same time."
             )
 
+        self._forward_impl = linear_with_grad_accumulation_and_async_allreduce
 
-    def forward(self, input_):
+    def forward(self, input_: torch.Tensor, weight: Optional[torch.Tensor] = None):
         """Forward of ColumnParallelLinear
 
         Args:
             input_: 3D tensor whose order of dimension is [sequence, batch, hidden]
 
+            weight (optional): weight tensor to use, compulsory when
+                skip_weight_param_allocation is True.
+
         Returns:
             - output
             - bias
+
         """
+        if weight is None:
+            if self.weight is None:
+                raise RuntimeError(
+                    "weight was not supplied to ColumnParallelLinear forward pass "
+                    "and skip_weight_param_allocation is True."
+                )
+            weight = self.weight
+        else:
+            # Check the weight passed in is the correct shape
+            expected_shape = (self.output_size_per_partition, self.input_size)
+            if weight.shape != expected_shape:
+                raise RuntimeError(
+                    f"supplied weight's shape is {tuple(weight.shape)}, "
+                    f"not {expected_shape} as expected"
+                )
+
         bias = self.bias if not self.skip_bias_add else None
 
-        if self.async_tensor_model_parallel_allreduce or \
-                self.sequence_parallel_enabled:
+        if self.async_tensor_model_parallel_allreduce or self.sequence_parallel:
             input_parallel = input_
         else:
             input_parallel = copy_to_tensor_model_parallel_region(input_)
         # Matrix multiply.
-        output_parallel = linear_with_grad_accumulation_and_async_allreduce(
+        if not weight.requires_grad:
+            self._forward_impl = linear_with_frozen_weight
+        else:
+            self._forward_impl = linear_with_grad_accumulation_and_async_allreduce
+        output_parallel = self._forward_impl(
             input=input_parallel,
-            weight=self.weight,
+            weight=weight,
             bias=bias,
             gradient_accumulation_fusion=self.gradient_accumulation_fusion,
             async_grad_allreduce=self.async_tensor_model_parallel_allreduce,
-            sequence_parallel_enabled=self.sequence_parallel_enabled,
+            sequence_parallel=self.sequence_parallel,
         )
         if self.gather_output:
             # All-gather across the partitions.
-            assert not self.sequence_parallel_enabled
+            assert not self.sequence_parallel
             output = gather_from_tensor_model_parallel_region(output_parallel)
         else:
             output = output_parallel
@@ -601,27 +761,27 @@ class RowParallelLinear(torch.nn.Module):
         keep_master_weight_for_test: This was added for testing and should be
                                      set to False. It returns the master weights
                                      used for initialization.
-        skip_bias_add: This was added to enable performance optimization where bias
-                       can be fused with other elementwise operations. We skip
-                       adding bias but instead return it.
-        params_dtype:
-        use_cpu_initialization:
-        perform_initialization:
-        gradient_accumulation_fusion:
-        sequence_parallel_enabled:
+        skip_bias_add: If True, do not add the bias term, instead
+                       return it to be added by the caller. This
+                       enables performance optimations where bias can
+                       be fused with other elementwise operations.
+        config: ModelParallelConfig object
+
     """
 
-    def __init__(self, input_size, output_size, *,
-                 bias=True, input_is_parallel=False,
-                 init_method=init.xavier_normal_, stride=1,
-                 keep_master_weight_for_test=False,
-                 skip_bias_add=False,
-                 params_dtype=torch.float32,
-                 use_cpu_initialization=False,
-                 perform_initialization=True,
-                 gradient_accumulation_fusion=False,
-                 sequence_parallel_enabled: bool = False,
-                 ):
+    def __init__(
+        self,
+        input_size: int,
+        output_size: int,
+        *,
+        config: ModelParallelConfig,
+        init_method: Callable,
+        bias: bool = True,
+        input_is_parallel: bool = False,
+        stride: int = 1,
+        keep_master_weight_for_test: bool = False,
+        skip_bias_add: bool = False,
+    ):
         super(RowParallelLinear, self).__init__()
 
         # Keep input parameters
@@ -632,49 +792,68 @@ class RowParallelLinear(torch.nn.Module):
         world_size = get_tensor_model_parallel_world_size()
         self.input_size_per_partition = divide(input_size, world_size)
         self.skip_bias_add = skip_bias_add
-        self.gradient_accumulation_fusion = gradient_accumulation_fusion
-        self.sequence_parallel_enabled = sequence_parallel_enabled
-        if self.sequence_parallel_enabled and not self.input_is_parallel:
-            raise RuntimeError("To enable `sequence_parallel_enabled`, `input_is_parallel` must be `True`")
+        self.config = config
+        self.gradient_accumulation_fusion = config.gradient_accumulation_fusion
+        self.sequence_parallel = config.sequence_parallel
+        if self.sequence_parallel and not self.input_is_parallel:
+            raise RuntimeError("To enable `sequence_parallel`, `input_is_parallel` must be `True`")
 
         # Parameters.
         # Note: torch.nn.functional.linear performs XA^T + b and as a result
         # we allocate the transpose.
         # Initialize weight.
-        if use_cpu_initialization:
-            self.weight = Parameter(torch.empty(self.output_size,
-                                                self.input_size_per_partition,
-                                                dtype=params_dtype))
-            if perform_initialization:
+        if config.use_cpu_initialization:
+            self.weight = Parameter(
+                torch.empty(
+                    self.output_size, self.input_size_per_partition, dtype=config.params_dtype
+                )
+            )
+            if config.perform_initialization:
                 self.master_weight = _initialize_affine_weight_cpu(
-                    self.weight, self.output_size, self.input_size,
-                    self.input_size_per_partition, 1, init_method,
-                    stride=stride, return_master_weight=keep_master_weight_for_test,
-                    params_dtype=params_dtype)
+                    self.weight,
+                    self.output_size,
+                    self.input_size,
+                    self.input_size_per_partition,
+                    1,
+                    init_method,
+                    stride=stride,
+                    return_master_weight=keep_master_weight_for_test,
+                    params_dtype=config.params_dtype,
+                )
         else:
-            self.weight = Parameter(torch.empty(
-                self.output_size, self.input_size_per_partition,
-                device=torch.cuda.current_device(), dtype=params_dtype))
-            if perform_initialization:
-                _initialize_affine_weight_gpu(self.weight, init_method,
-                                              partition_dim=1, stride=stride)
+            self.weight = Parameter(
+                torch.empty(
+                    self.output_size,
+                    self.input_size_per_partition,
+                    device=torch.cuda.current_device(),
+                    dtype=config.params_dtype,
+                )
+            )
+            if config.perform_initialization:
+                _initialize_affine_weight_gpu(
+                    self.weight, init_method, partition_dim=1, stride=stride
+                )
         if bias:
-            if use_cpu_initialization:
-                self.bias = Parameter(torch.empty(self.output_size,
-                                                  dtype=params_dtype))
+            if config.use_cpu_initialization:
+                self.bias = Parameter(torch.empty(self.output_size, dtype=config.params_dtype))
             else:
-                self.bias = Parameter(torch.empty(
-                    self.output_size, device=torch.cuda.current_device(),
-                    dtype=params_dtype))
-            setattr(self.bias, 'sequence_parallel', sequence_parallel_enabled)
-
-            # Always initialize bias to zero.
-            with torch.no_grad():
-                self.bias.zero_()
+                self.bias = Parameter(
+                    torch.empty(
+                        self.output_size,
+                        device=torch.cuda.current_device(),
+                        dtype=config.params_dtype,
+                    )
+                )
+            setattr(self.bias, 'sequence_parallel', self.sequence_parallel)
+
+            if config.perform_initialization:
+                # Always initialize bias to zero.
+                with torch.no_grad():
+                    self.bias.zero_()
         else:
             self.register_parameter('bias', None)
 
-
+        self._forward_impl = linear_with_grad_accumulation_and_async_allreduce
 
     def forward(self, input_):
         """Forward of RowParallelLinear
@@ -690,20 +869,24 @@ class RowParallelLinear(torch.nn.Module):
         if self.input_is_parallel:
             input_parallel = input_
         else:
-            assert not self.sequence_parallel_enabled
+            assert not self.sequence_parallel
             input_parallel = scatter_to_tensor_model_parallel_region(input_)
         # Matrix multiply.
-        output_parallel = linear_with_grad_accumulation_and_async_allreduce(
+        if not self.weight.requires_grad:
+            self._forward_impl = linear_with_frozen_weight
+        else:
+            self._forward_impl = linear_with_grad_accumulation_and_async_allreduce
+        output_parallel = self._forward_impl(
             input=input_parallel,
             weight=self.weight,
             bias=None,
             gradient_accumulation_fusion=self.gradient_accumulation_fusion,
             async_grad_allreduce=False,
-            sequence_parallel_enabled=False,
+            sequence_parallel=False,
         )
 
         # All-reduce across all the partitions.
-        if self.sequence_parallel_enabled:
+        if self.sequence_parallel:
             output_ = reduce_scatter_to_sequence_parallel_region(output_parallel)
         else:
             output_ = reduce_from_tensor_model_parallel_region(output_parallel)

megatron/core/tensor_parallel/mappings.py

@@ -3,10 +3,11 @@
 import torch
 
 from megatron.core.parallel_state import (
+    get_tensor_model_parallel_group,
     get_tensor_model_parallel_rank,
     get_tensor_model_parallel_world_size,
-    get_tensor_model_parallel_group,
 )
+
 from .utils import split_tensor_along_last_dim
 
 
@@ -14,7 +15,7 @@ def _reduce(input_):
     """All-reduce the input tensor across model parallel group."""
 
     # Bypass the function if we are using only 1 GPU.
-    if get_tensor_model_parallel_world_size()==1:
+    if get_tensor_model_parallel_world_size() == 1:
         return input_
 
     # All-reduce.
@@ -53,13 +54,14 @@ def _split_along_first_dim(input_):
 
     # Split along first dimension.
     dim_size = input_.size()[0]
-    assert dim_size % world_size == 0, \
-        "First dimension of the tensor should be divisible by tensor parallel size"
+    assert (
+        dim_size % world_size == 0
+    ), "First dimension of the tensor should be divisible by tensor parallel size"
     local_dim_size = dim_size // world_size
     rank = get_tensor_model_parallel_rank()
     dim_offset = rank * local_dim_size
 
-    output = input_[dim_offset:dim_offset+local_dim_size].contiguous()
+    output = input_[dim_offset : dim_offset + local_dim_size].contiguous()
 
     return output
 
@@ -97,13 +99,14 @@ def _gather_along_first_dim(input_):
     dim_size = list(input_.size())
     dim_size[0] = dim_size[0] * world_size
 
-    output = torch.empty(dim_size, dtype=input_.dtype,
-                         device=torch.cuda.current_device())
-    torch.distributed._all_gather_base(output, input_.contiguous(),
-                                       group=get_tensor_model_parallel_group())
+    output = torch.empty(dim_size, dtype=input_.dtype, device=torch.cuda.current_device())
+    torch.distributed._all_gather_base(
+        output, input_.contiguous(), group=get_tensor_model_parallel_group()
+    )
 
     return output
 
+
 def _reduce_scatter_along_first_dim(input_):
     """Reduce-scatter the input tensor across model parallel group."""
     world_size = get_tensor_model_parallel_world_size()
@@ -112,15 +115,16 @@ def _reduce_scatter_along_first_dim(input_):
         return input_
 
     dim_size = list(input_.size())
-    assert dim_size[0] % world_size == 0, \
-        "First dimension of the tensor should be divisible by tensor parallel size"
-    
+    assert (
+        dim_size[0] % world_size == 0
+    ), "First dimension of the tensor should be divisible by tensor parallel size"
+
     dim_size[0] = dim_size[0] // world_size
-   
-    output = torch.empty(dim_size, dtype=input_.dtype,
-                         device=torch.cuda.current_device())
-    torch.distributed._reduce_scatter_base(output, input_.contiguous(), 
-                                           group=get_tensor_model_parallel_group())
+
+    output = torch.empty(dim_size, dtype=input_.dtype, device=torch.cuda.current_device())
+    torch.distributed._reduce_scatter_base(
+        output, input_.contiguous(), group=get_tensor_model_parallel_group()
+    )
     return output
 
 
@@ -130,7 +134,7 @@ class _CopyToModelParallelRegion(torch.autograd.Function):
     @staticmethod
     def symbolic(graph, input_):
         return input_
-    
+
     @staticmethod
     def forward(ctx, input_):
         return input_
@@ -146,7 +150,7 @@ class _ReduceFromModelParallelRegion(torch.autograd.Function):
     @staticmethod
     def symbolic(graph, input_):
         return _reduce(input_)
-    
+
     @staticmethod
     def forward(ctx, input_):
         return _reduce(input_)
@@ -178,7 +182,7 @@ class _GatherFromModelParallelRegion(torch.autograd.Function):
     @staticmethod
     def symbolic(graph, input_):
         return _gather_along_last_dim(input_)
-    
+
     @staticmethod
     def forward(ctx, input_):
         return _gather_along_last_dim(input_)
@@ -205,12 +209,12 @@ class _ScatterToSequenceParallelRegion(torch.autograd.Function):
 
 
 class _GatherFromSequenceParallelRegion(torch.autograd.Function):
-    """Gather the input from sequence parallel region and concatinate.""" 
+    """Gather the input from sequence parallel region and concatinate."""
 
     @staticmethod
     def symbolic(graph, input_, tensor_parallel_output_grad=True):
         return _gather_along_first_dim(input_)
-    
+
     @staticmethod
     def forward(ctx, input_, tensor_parallel_output_grad=True):
         ctx.tensor_parallel_output_grad = tensor_parallel_output_grad
@@ -221,8 +225,8 @@ class _GatherFromSequenceParallelRegion(torch.autograd.Function):
         tensor_parallel_output_grad = ctx.tensor_parallel_output_grad
 
         # If the computation graph after the gather operation is
-        # in the tensor parallel mode, output gradients need to reduce 
-        # scattered and whereas if the computation is duplicated, 
+        # in the tensor parallel mode, output gradients need to reduce
+        # scattered and whereas if the computation is duplicated,
         # output gradients need to be scattered.
         if tensor_parallel_output_grad:
             return _reduce_scatter_along_first_dim(grad_output), None
@@ -236,7 +240,7 @@ class _ReduceScatterToSequenceParallelRegion(torch.autograd.Function):
     @staticmethod
     def symbolic(graph, input_):
         return _reduce_scatter_along_first_dim(input_)
-    
+
     @staticmethod
     def forward(ctx, input_):
         return _reduce_scatter_along_first_dim(input_)
@@ -250,6 +254,7 @@ class _ReduceScatterToSequenceParallelRegion(torch.autograd.Function):
 # Helper functions.
 # -----------------
 
+
 def copy_to_tensor_model_parallel_region(input_):
     return _CopyToModelParallelRegion.apply(input_)
 
@@ -276,4 +281,3 @@ def gather_from_sequence_parallel_region(input_, tensor_parallel_output_grad=Tru
 
 def reduce_scatter_to_sequence_parallel_region(input_):
     return _ReduceScatterToSequenceParallelRegion.apply(input_)
-

megatron/core/tensor_parallel/random.py

@@ -7,7 +7,8 @@ import contextlib
 
 import torch
 from torch import _C
-from torch.cuda import _lazy_call, device as device_ctx_manager
+from torch.cuda import _lazy_call
+from torch.cuda import device as device_ctx_manager
 from torch.utils.checkpoint import detach_variable
 
 from megatron.core.parallel_state import (
@@ -16,14 +17,10 @@ from megatron.core.parallel_state import (
     get_tensor_model_parallel_rank,
     get_tensor_model_parallel_world_size,
 )
-
-from .utils import (
-    split_tensor_into_1d_equal_chunks,
-    gather_split_1d_tensor,
-)
-
 from megatron.core.utils import safely_set_viewless_tensor_data
 
+from .utils import gather_split_1d_tensor, split_tensor_into_1d_equal_chunks
+
 # Default name for the model parallel rng tracker.
 _MODEL_PARALLEL_RNG_TRACKER_NAME = 'model-parallel-rng'
 
@@ -42,6 +39,7 @@ def _set_cuda_rng_state(new_state, device=-1):
         def cb():
             with device_ctx_manager(device):
                 _C._cuda_setRNGState(new_state)
+
     else:
         # newer PyTorch
         if device == -1:
@@ -61,7 +59,6 @@ def _set_cuda_rng_state(new_state, device=-1):
     _lazy_call(cb)
 
 
-
 class CudaRNGStatesTracker:
     """Tracker for the cuda RNG states.
 
@@ -169,8 +166,7 @@ def model_parallel_cuda_manual_seed(seed):
     # Set the default state.
     torch.cuda.manual_seed(data_parallel_seed)
     # and model parallel state.
-    _CUDA_RNG_STATE_TRACKER.add(_MODEL_PARALLEL_RNG_TRACKER_NAME,
-                                tensor_model_parallel_seed)
+    _CUDA_RNG_STATE_TRACKER.add(_MODEL_PARALLEL_RNG_TRACKER_NAME, tensor_model_parallel_seed)
 
 
 class CheckpointFunction(torch.autograd.Function):
@@ -180,11 +176,11 @@ class CheckpointFunction(torch.autograd.Function):
            2) the states in the model parallel tracker are also properly
               tracked/set/reset.
     """
+
     @staticmethod
     def forward(ctx, run_function, distribute_saved_activations, *args):
         ctx.run_function = run_function
-        ctx.distribute_saved_activations \
-            = distribute_saved_activations
+        ctx.distribute_saved_activations = distribute_saved_activations
 
         # Copy the rng states.
         ctx.fwd_cpu_rng_state = torch.get_rng_state()
@@ -199,8 +195,8 @@ class CheckpointFunction(torch.autograd.Function):
         if distribute_saved_activations:
             ctx.input_0_shape = args[0].data.shape
             safely_set_viewless_tensor_data(
-                args[0],
-                split_tensor_into_1d_equal_chunks(args[0].data, new_buffer=True))
+                args[0], split_tensor_into_1d_equal_chunks(args[0].data, new_buffer=True)
+            )
 
         # Store everything.
         ctx.save_for_backward(*args)
@@ -210,13 +206,15 @@ class CheckpointFunction(torch.autograd.Function):
     @staticmethod
     def backward(ctx, *args):
         if not torch.autograd._is_checkpoint_valid():
-            raise RuntimeError("Checkpointing is not compatible with .grad(), "
-                               "please use .backward() if possible")
+            raise RuntimeError(
+                "Checkpointing is not compatible with .grad(), "
+                "please use .backward() if possible"
+            )
         inputs = ctx.saved_tensors
         if ctx.distribute_saved_activations:
             safely_set_viewless_tensor_data(
-                inputs[0],
-                gather_split_1d_tensor(inputs[0].data).view(ctx.input_0_shape))
+                inputs[0], gather_split_1d_tensor(inputs[0].data).view(ctx.input_0_shape)
+            )
 
         # Store the current states.
         bwd_cpu_rng_state = torch.get_rng_state()
@@ -241,13 +239,11 @@ class CheckpointFunction(torch.autograd.Function):
         if isinstance(outputs, torch.Tensor):
             outputs = (outputs,)
         torch.autograd.backward(outputs, args)
-        grads = tuple(inp.grad if isinstance(inp, torch.Tensor) else inp
-                      for inp in detached_inputs)
+        grads = tuple(inp.grad if isinstance(inp, torch.Tensor) else inp for inp in detached_inputs)
         return (None, None) + grads
 
 
 def checkpoint(function, distribute_saved_activations, *args):
     """Checkpoint a model or part of the model.
     This has been directly copied from torch.utils.checkpoint."""
-    return CheckpointFunction.apply(function,
-                                    distribute_saved_activations, *args)
+    return CheckpointFunction.apply(function, distribute_saved_activations, *args)

megatron/core/tensor_parallel/utils.py

 # Copyright (c) 2022, NVIDIA CORPORATION. All rights reserved.
 
-import torch
 from typing import List, Sequence
 
-from megatron.core.utils import divide
+import torch
+
 from megatron.core import parallel_state
+from megatron.core.utils import divide
+
 
 def split_tensor_along_last_dim(
-    tensor: torch.Tensor,
-    num_partitions: int,
-    contiguous_split_chunks: bool = False,
+    tensor: torch.Tensor, num_partitions: int, contiguous_split_chunks: bool = False,
 ) -> List[torch.Tensor]:
     """ Split a tensor along its last dimension.
 
@@ -33,6 +33,7 @@ def split_tensor_along_last_dim(
 
     return tensor_list
 
+
 def split_tensor_into_1d_equal_chunks(tensor, new_buffer=False):
     """ Break a tensor into equal 1D chunks across tensor parallel ranks.
 
@@ -47,14 +48,16 @@ def split_tensor_into_1d_equal_chunks(tensor, new_buffer=False):
                                Default is False
 
     """
-    partition_size = torch.numel(tensor) // \
-        parallel_state.get_tensor_model_parallel_world_size()
+    partition_size = torch.numel(tensor) // parallel_state.get_tensor_model_parallel_world_size()
     start_index = partition_size * parallel_state.get_tensor_model_parallel_rank()
     end_index = start_index + partition_size
     if new_buffer:
-        data = torch.empty(partition_size, dtype=tensor.dtype,
-                           device=torch.cuda.current_device(),
-                           requires_grad=False)
+        data = torch.empty(
+            partition_size,
+            dtype=tensor.dtype,
+            device=torch.cuda.current_device(),
+            requires_grad=False,
+        )
         data.copy_(tensor.view(-1)[start_index:end_index])
     else:
         data = tensor.view(-1)[start_index:end_index]
@@ -70,18 +73,18 @@ def gather_split_1d_tensor(tensor):
         Arguments:
             tensor: A Tensor or view of this rank's portion of the data.
     """
-    numel_gathered = torch.numel(tensor) * \
-        parallel_state.get_tensor_model_parallel_world_size()
-    gathered = torch.empty(numel_gathered, dtype=tensor.dtype,
-                           device=torch.cuda.current_device(),
-                           requires_grad=False)
+    numel_gathered = torch.numel(tensor) * parallel_state.get_tensor_model_parallel_world_size()
+    gathered = torch.empty(
+        numel_gathered, dtype=tensor.dtype, device=torch.cuda.current_device(), requires_grad=False
+    )
     # TODO: This API is experimental in pytorch (as of Feb 2022) and
     # this might break in future pytorch releases. We chose this API
     # as opposed to torch.distributed.all_gather for efficiency reasons.
     # This API calls directly NCCL all-gather versus the former does
     # internal copies and can potentially cause slow down.
-    torch.distributed._all_gather_base(gathered, tensor,
-                                       group=parallel_state.get_tensor_model_parallel_group())
+    torch.distributed._all_gather_base(
+        gathered, tensor, group=parallel_state.get_tensor_model_parallel_group()
+    )
     return gathered
 
 
@@ -101,7 +104,9 @@ class VocabUtility:
         return index_f, index_l
 
     @staticmethod
-    def vocab_range_from_global_vocab_size(global_vocab_size: int, rank: int, world_size: int) -> Sequence[int]:
+    def vocab_range_from_global_vocab_size(
+        global_vocab_size: int, rank: int, world_size: int
+    ) -> Sequence[int]:
         per_partition_vocab_size = divide(global_vocab_size, world_size)
         return VocabUtility.vocab_range_from_per_partition_vocab_size(
             per_partition_vocab_size, rank, world_size

megatron/core/transformer/__init__.py

+# Copyright (c) 2023, NVIDIA CORPORATION. All rights reserved.
+
+from .transformer_config import TransformerConfig

megatron/core/transformer/attention.py

+# Copyright (c) 2023, NVIDIA CORPORATION. All rights reserved.
+
+from abc import ABC, abstractmethod
+
+import torch
+
+from megatron.core import parallel_state, tensor_parallel
+from megatron.core.models.common.rotary_pos_embedding import apply_rotary_pos_emb
+from megatron.core.transformer.custom_layers.transformer_engine import (
+    TEDotProductAttention,
+    TELayerNormColumnParallelLinear,
+    TERowParallelLinear,
+)
+from megatron.core.transformer.enums import AttnMaskType
+from megatron.core.transformer.module import MegatronModule
+from megatron.core.transformer.transformer_config import TransformerConfig
+from megatron.core.utils import divide
+
+from .enums import AttnMaskType
+from .transformer_config import TransformerConfig
+
+
+class Attention(MegatronModule, ABC):
+    """Attention layer abstract class.
+
+    This layer only contains common modules required for the "self attn" and
+    "cross attn" specializations.
+    """
+
+    def __init__(
+        self, config: TransformerConfig, layer_number: int = 1, attn_mask_type=AttnMaskType.padding,
+    ):
+        super().__init__(config=config)
+
+        self.config = config
+        self.layer_number = layer_number
+        self.attn_mask_type = attn_mask_type
+
+        # For normal attention without groups, num_query_groups == num_attention_heads,
+        # so these two will be the same
+        self.query_projection_size = self.config.kv_channels * self.config.num_attention_heads
+        self.kv_projection_size = self.config.kv_channels * self.config.num_query_groups
+
+        # Per attention head and per partition values.
+        world_size = parallel_state.get_tensor_model_parallel_world_size()
+        self.hidden_size_per_attention_head = divide(
+            self.query_projection_size, self.config.num_attention_heads
+        )
+        self.num_attention_heads_per_partition = divide(self.config.num_attention_heads, world_size)
+        self.num_query_groups_per_partition = divide(self.config.num_query_groups, world_size)
+
+        self.dot_product_attention = TEDotProductAttention(
+            config=self.config, layer_number=self.layer_number, attn_mask_type=self.attn_mask_type
+        )
+
+        self.checkpoint_dot_product_attention = self.config.recompute_granularity == 'selective'
+
+        # Output.
+        self.linear_proj = TERowParallelLinear(
+            self.query_projection_size,
+            self.config.hidden_size,
+            config=self.config,
+            init_method=self.config.output_layer_init_method,
+            bias=self.config.add_bias_linear,
+            skip_bias_add=True,
+        )
+
+    def _checkpointed_attention_forward(
+        self, query, key, value, attention_mask, rotary_pos_emb=None
+    ):
+        """Forward method with selective activation checkpointing."""
+
+        def custom_forward(*inputs):
+            query = inputs[0]
+            key = inputs[1]
+            value = inputs[2]
+            attention_mask = inputs[3]
+            output_ = self.dot_product_attention(query, key, value, attention_mask)
+            return output_
+
+        hidden_states = tensor_parallel.checkpoint(
+            custom_forward, False, query, key, value, attention_mask, rotary_pos_emb
+        )
+
+        return hidden_states
+
+    def _allocate_memory(self, inference_max_sequence_length, batch_size, dtype):
+        """Allocate memory to store kv cache during inference."""
+
+        return torch.empty(
+            inference_max_sequence_length,
+            batch_size,
+            self.num_query_groups_per_partition,
+            self.hidden_size_per_attention_head,
+            dtype=dtype,
+            device=torch.cuda.current_device(),
+        )
+
+    def _adjust_key_value_for_inference(self, inference_params, key, value, rotary_pos_emb):
+        """
+        Saves the generated key and value tensors to the end of the buffers in inference_params.
+        Returns the full size keys and values from the provided inference_params, as well as
+        adjusted rotary_pos_emb.
+
+        Returns a tuple: (key, value, rotary_pos_emb)
+
+        """
+        if inference_params is None:
+            return key, value, rotary_pos_emb
+
+        # =================================================
+        # Pre-allocate memory for key-values for inference.
+        # =================================================
+        is_first_step = False
+        if self.layer_number not in inference_params.key_value_memory_dict:
+            inf_max_seq_length = inference_params.max_sequence_length
+            inf_max_batch_size = inference_params.max_batch_size
+            inference_key_memory = self._allocate_memory(
+                inf_max_seq_length, inf_max_batch_size, key.dtype
+            )
+            inference_value_memory = self._allocate_memory(
+                inf_max_seq_length, inf_max_batch_size, value.dtype
+            )
+            inference_params.key_value_memory_dict[self.layer_number] = (
+                inference_key_memory,
+                inference_value_memory,
+            )
+            is_first_step = True
+        else:
+            # Get the pre-allocated buffers for this layer
+            inference_key_memory, inference_value_memory = inference_params.key_value_memory_dict[
+                self.layer_number
+            ]
+
+        batch_start = inference_params.batch_size_offset
+        batch_end = batch_start + key.size(1)
+        assert batch_end <= inference_key_memory.size(1)
+        sequence_start = inference_params.sequence_len_offset
+        sequence_end = sequence_start + key.size(0)
+        assert sequence_end <= inference_key_memory.size(0)
+        # Copy key and values.
+        inference_key_memory[sequence_start:sequence_end, batch_start:batch_end, ...] = key
+        inference_value_memory[sequence_start:sequence_end, batch_start:batch_end, ...] = value
+        key = inference_key_memory[:sequence_end, batch_start:batch_end, ...]
+        value = inference_value_memory[:sequence_end, batch_start:batch_end, ...]
+
+        # adjust the key rotary positional embedding
+        if rotary_pos_emb is not None:
+            q_pos_emb, k_pos_emb = rotary_pos_emb
+            # need to cross check this condition during inference
+            # if not set_inference_key_value_memory:
+            if not is_first_step:
+                # In inference, we compute one token at a time.
+                # Select the correct positional embedding
+                # (only the last token in the sequence)
+                q_pos_emb = q_pos_emb[sequence_end - 1 : sequence_end]
+            else:
+                # In the first forward pass of inference,
+                # we use the entire provided prefix.
+                # q_pos_emb here has the rope embeddings of the entire
+                # prefix + to-be-generated output so
+                # we slice to just the prefix.
+                q_pos_emb = q_pos_emb[:sequence_end, :, :, :]
+            k_pos_emb = k_pos_emb[:sequence_end, :, :, :]
+            rotary_pos_emb = (q_pos_emb, k_pos_emb)
+
+        return key, value, rotary_pos_emb
+
+    @abstractmethod
+    def get_query_key_value_tensors(self, hidden_states, key_value_states):
+        """
+        This method needs to be implemented based on whether the derived class
+        is "self-attn" or "cross-attn".
+        """
+
+    def forward(
+        self,
+        hidden_states,
+        attention_mask,
+        key_value_states=None,
+        inference_params=None,
+        rotary_pos_emb=None,
+    ):
+        # hidden_states: [sq, b, h]
+
+        # For self attention we just duplicate the rotary_pos_emb if it isn't already
+        if rotary_pos_emb is not None and not isinstance(rotary_pos_emb, tuple):
+            rotary_pos_emb = (rotary_pos_emb,) * 2
+
+        # =====================
+        # Query, Key, and Value
+        # =====================
+        # Get the query, key and value tensors based on the type of attention -
+        # self or cross attn.
+        query, key, value = self.get_query_key_value_tensors(hidden_states, key_value_states)
+
+        # ===================================================
+        # Adjust key, value, and rotary_pos_emb for inference
+        # ===================================================
+        key, value, rotary_pos_emb = self._adjust_key_value_for_inference(
+            inference_params, key, value, rotary_pos_emb
+        )
+
+        # ================================================
+        # relative positional embedding (rotary embedding)
+        # ================================================
+        if rotary_pos_emb is not None:
+            q_pos_emb, k_pos_emb = rotary_pos_emb
+            query = apply_rotary_pos_emb(query, q_pos_emb)
+            key = apply_rotary_pos_emb(key, k_pos_emb)
+            # TODO, can apply positional embedding to value_layer so it has
+            # absolute positional embedding.
+            # otherwise, only relative positional embedding takes effect
+            # value_layer = apply_rotary_pos_emb(value_layer, k_pos_emb)
+
+        # ==================================
+        # core attention computation
+        # ==================================
+
+        # expand the key_layer and value_layer [sk, b, ng, hn] -> [sk, b, np, hn]
+        # This is a noop for normal attention where ng == np. When using group query attention this
+        # creates a view that has the keys and values virtually repeated along their dimension to
+        # match the number of queries.
+        if self.num_attention_heads_per_partition // self.num_query_groups_per_partition > 1:
+            key = key.repeat_interleave(
+                self.num_attention_heads_per_partition // self.num_query_groups_per_partition, dim=2
+            )
+            value = value.repeat_interleave(
+                self.num_attention_heads_per_partition // self.num_query_groups_per_partition, dim=2
+            )
+
+        if self.checkpoint_dot_product_attention:
+            core_attn_out = self._checkpointed_attention_forward(query, key, value, attention_mask)
+        else:
+            core_attn_out = self.dot_product_attention(query, key, value, attention_mask)
+
+        # =================
+        # Output. [sq, b, h]
+        # =================
+
+        output, bias = self.linear_proj(core_attn_out)
+
+        return output, bias
+
+
+class SelfAttention(Attention):
+    """Self-attention layer class
+
+    Self-attention layer takes input with size [s, b, h]
+    and returns output of the same size.
+    """
+
+    def __init__(
+        self, config: TransformerConfig, layer_number: int = 1, attn_mask_type=AttnMaskType.padding
+    ):
+        super().__init__(config=config, layer_number=layer_number, attn_mask_type=attn_mask_type)
+
+        self.linear_qkv = TELayerNormColumnParallelLinear(
+            self.config.hidden_size,
+            self.query_projection_size + 2 * self.kv_projection_size,
+            config=self.config,
+            init_method=self.config.init_method,
+            bias=self.config.add_bias_linear,
+            skip_bias_add=False,
+        )
+
+    def get_query_key_value_tensors(self, hidden_states, key_value_states=None):
+        """
+        Derives `query`, `key` and `value` tensors from `hidden_states`.
+        """
+        # Attention heads [sq, b, h] --> [sq, b, ng * (np/ng + 2) * hn)]
+        mixed_qkv, _ = self.linear_qkv(hidden_states)
+
+        # [sq, b, hp] --> [sq, b, ng, (np/ng + 2) * hn]
+        new_tensor_shape = mixed_qkv.size()[:-1] + (
+            self.num_query_groups_per_partition,
+            (
+                (self.num_attention_heads_per_partition // self.num_query_groups_per_partition + 2)
+                * self.hidden_size_per_attention_head
+            ),
+        )
+        mixed_qkv = mixed_qkv.view(*new_tensor_shape)
+
+        # [sq, b, ng, (np/ng + 2) * hn] --> [sq, b, ng, np/ng * hn], [sq, b, ng, hn], [sq, b, ng, hn]
+        (query, key, value) = torch.split(
+            mixed_qkv,
+            [
+                (
+                    self.num_attention_heads_per_partition
+                    // self.num_query_groups_per_partition
+                    * self.hidden_size_per_attention_head
+                ),
+                self.hidden_size_per_attention_head,
+                self.hidden_size_per_attention_head,
+            ],
+            dim=3,
+        )
+        # [sq, b, ng, np/ng * hn] -> [sq, b, np, hn]
+        query = query.reshape(query.size(0), query.size(1), -1, self.hidden_size_per_attention_head)
+
+        return query, key, value
+
+
+class CrossAttention(Attention):
+    """Cross-attention layer class
+
+    Cross-attention layer takes input with size [s, b, h] and context with size
+    [s, b, h] and returns output of the same size.
+    """
+
+    def __init__(
+        self, config: TransformerConfig, layer_number: int = 1, attn_mask_type=AttnMaskType.padding
+    ):
+        super().__init__(config=config, layer_number=layer_number, attn_mask_type=attn_mask_type)
+
+        if self.config.num_query_groups != self.config.num_attention_heads:
+            raise ValueError(
+                f"Group query attention is not currently supported in cross attention."
+            )
+        assert self.query_projection_size == self.kv_projection_size
+
+        self.linear_q = TELayerNormColumnParallelLinear(
+            self.config.hidden_size,
+            self.query_projection_size,
+            config=self.config,
+            init_method=self.config.init_method,
+            bias=self.config.add_bias_linear,
+            skip_bias_add=False,
+        )
+
+        self.linear_kv = TELayerNormColumnParallelLinear(
+            self.config.hidden_size,
+            2 * self.kv_projection_size,
+            config=self.config,
+            init_method=self.config.init_method,
+            bias=self.config.add_bias_linear,
+            skip_bias_add=False,
+        )
+
+    def get_query_key_value_tensors(self, hidden_states, key_value_states):
+        """
+        Derives `query` tensor from `hidden_states`, and `key`/`value` tensors
+        from `key_value_states`.
+        """
+        # Attention heads [sk, b, h] --> [sk, b, (np * 2 * hn)]
+        mixed_kv, _ = self.linear_kv(key_value_states)
+
+        # [sk, b, (np * 2 * hn)] --> [sk, b, np, 2 * hn]
+        new_tensor_shape = mixed_kv.size()[:-1] + (
+            self.num_attention_heads_per_partition,
+            2 * self.hidden_size_per_attention_head,
+        )
+        mixed_kv = mixed_kv.view(*new_tensor_shape)
+
+        # [sk, b, np, 2 * hn] --> 2 [sk, b, np, hn]
+        (key, value) = tensor_parallel.split_tensor_along_last_dim(mixed_kv, 2)
+
+        # Attention head [sq, b, h] --> [sq, b, hp]
+        query, _ = self.linear_q(hidden_states)
+
+        # [sq, b, hp] --> [sq, b, np, hn]
+        new_tensor_shape = query.size()[:-1] + (
+            self.num_attention_heads_per_partition,
+            self.hidden_size_per_attention_head,
+        )
+        query = query.view(*new_tensor_shape)
+
+        return query, key, value

megatron/core/transformer/custom_layers/transformer_engine.py

+from importlib.metadata import version
+from typing import Callable
+
+import torch
+import transformer_engine as te
+from pkg_resources import packaging
+
+from megatron.core.parallel_state import get_tensor_model_parallel_group
+from megatron.core.tensor_parallel import get_cuda_rng_tracker
+from megatron.core.transformer.enums import AttnMaskType
+from megatron.core.transformer.transformer_config import TransformerConfig
+
+
+def _get_extra_te_kwargs(config: TransformerConfig):
+    extra_transformer_engine_kwargs = {}
+    from importlib.metadata import version
+
+    from pkg_resources import packaging
+
+    te_version = packaging.version.Version(version("transformer-engine"))
+    if te_version >= packaging.version.Version("0.12.0"):
+        if config.use_cpu_initialization:
+            extra_transformer_engine_kwargs["device"] = 'cpu'
+        else:
+            extra_transformer_engine_kwargs["device"] = torch.cuda.current_device()
+    return extra_transformer_engine_kwargs
+
+
+class TENorm:
+    """
+    A conditional wrapper to initialize an instance of Transformer-Engine's
+    `LayerNorm` or `RMSNorm` based on input
+    """
+
+    def __new__(
+        cls,
+        config: TransformerConfig,
+        hidden_size: int,
+        eps: float = 1e-5,
+        sequence_parallel: bool = False,
+        normalization="LayerNorm",
+        **kwargs
+    ):
+        zero_centered_gamma = kwargs.get('zero_centered_gamma', False)
+        if normalization == "LayerNorm":
+            instance = te.pytorch.LayerNorm(
+                hidden_size=hidden_size,
+                eps=eps,
+                sequence_parallel=sequence_parallel,
+                zero_centered_gamma=zero_centered_gamma,
+                **_get_extra_te_kwargs(config),
+            )
+        elif normalization == "RMSNorm":
+            assert hasattr(
+                te.pytorch, "RMSNorm"
+            ), "Transformer-Engine >= v0.11 required to use this feature"
+            instance = te.pytorch.RMSNorm(
+                hidden_size=hidden_size,
+                eps=eps,
+                sequence_parallel=sequence_parallel,
+                zero_centered_gamma=zero_centered_gamma,
+                **_get_extra_te_kwargs(config),
+            )
+        else:
+            raise Exception('Only LayerNorm and RMSNorm are curently supported')
+
+        return instance
+
+
+class TELinear(te.pytorch.Linear):
+    """
+    Wrapper for the Transformer-Engine's `Linear` layer.
+
+    Note that if Megatron's parallel_state has not been initialized
+    yet, the tp_group passed to TE will be None and must be set later
+    via set_tensor_parallel_group().
+    """
+
+    def __init__(
+        self,
+        input_size: int,
+        output_size: int,
+        config: TransformerConfig,
+        parallel_mode: str,
+        init_method: Callable,
+        *,
+        bias: bool = True,
+        skip_bias_add: bool = False,
+        **kwargs
+    ):
+        self.config = config
+
+        # TE returns a zero length Tensor when bias=False and
+        # return_bias=True, but we prefer None.  So in that case we
+        # tell TE to not return the bias, and return None
+        # ourselves. This way our forward always returns two values
+        # and we don't have to deal with the zero length Tensor.
+        self.te_return_bias = skip_bias_add and bias
+
+        super().__init__(
+            in_features=input_size,
+            out_features=output_size,
+            sequence_parallel=self.config.sequence_parallel,
+            fuse_wgrad_accumulation=self.config.gradient_accumulation_fusion,
+            tp_group=get_tensor_model_parallel_group(check_initialized=False),
+            tp_size=self.config.tensor_model_parallel_size,
+            get_rng_state_tracker=get_cuda_rng_tracker,
+            init_method=init_method,
+            params_dtype=self.config.params_dtype,
+            parallel_mode=parallel_mode,
+            bias=bias,
+            return_bias=self.te_return_bias,
+            **_get_extra_te_kwargs(config),
+            **kwargs,
+        )
+
+    def forward(self, x):
+        out = super().forward(x)
+
+        # TE only returns a tuple when return_bias is True, otherwise
+        # it returns a single Tensor, we always want to return two
+        # values regardless of the arguments.
+        if self.te_return_bias:
+            return out
+        return out, None
+
+
+class TELayerNormColumnParallelLinear(te.pytorch.LayerNormLinear):
+    """
+    Wrapper for the Transformer-Engine's `LayerNormLinear` layer that combines
+    layernorm and linear layers
+    """
+
+    def __init__(
+        self,
+        input_size: int,
+        output_size: int,
+        config: TransformerConfig,
+        init_method: Callable,
+        bias: bool,
+        skip_bias_add: bool,
+        **kwargs
+    ):
+        self.config = config
+        # TE returns a zero length Tensor when bias=False and
+        # return_bias=True, but we prefer None.  So in that case we
+        # tell TE to not return the bias, and return None
+        # ourselves. This way our forward always returns two values
+        # and we don't have to deal with the zero length Tensor.
+        self.te_return_bias = skip_bias_add and bias
+
+        # Only Transformer-Engine version >= 0.11.0 supports `RMSNorm`
+        te_version = packaging.version.Version(version("transformer-engine"))
+        if te_version >= packaging.version.Version("0.11.0"):
+            kwargs["normalization"] = self.config.normalization
+
+        super().__init__(
+            in_features=input_size,
+            out_features=output_size,
+            bias=bias,
+            sequence_parallel=self.config.sequence_parallel,
+            fuse_wgrad_accumulation=self.config.gradient_accumulation_fusion,
+            tp_group=get_tensor_model_parallel_group(check_initialized=False),
+            tp_size=self.config.tensor_model_parallel_size,
+            get_rng_state_tracker=get_cuda_rng_tracker,
+            init_method=init_method,
+            params_dtype=self.config.params_dtype,
+            parallel_mode="column",
+            return_bias=self.te_return_bias,
+            zero_centered_gamma=self.config.layernorm_zero_centered_gamma,
+            **_get_extra_te_kwargs(config),
+            **kwargs,
+        )
+
+    def forward(self, x):
+        out = super().forward(x)
+
+        # TE only returns a tuple when return_bias is True, otherwise
+        # it returns a single Tensor, we always want to return two
+        # values regardless of the arguments.
+        if self.te_return_bias:
+            return out
+        return out, None
+
+
+class TEColumnParallelLinear(TELinear):
+    """
+    Wrapper for the Transformer-Engine's `Linear` layer but specialized similar
+    to megatron's `ColumnParallelLinear` layer.
+    """
+
+    def __init__(self, input_size: int, output_size: int, config: TransformerConfig, **kwargs):
+        self.config = config
+        super().__init__(
+            input_size=input_size,
+            output_size=output_size,
+            config=self.config,
+            parallel_mode="column",
+            **kwargs,
+        )
+
+
+class TERowParallelLinear(TELinear):
+    """
+    Wrapper for the Transformer-Engine's `Linear` layer but specialized similar
+    to megatron's `RowParallelLinear` layer.
+    """
+
+    def __init__(self, input_size: int, output_size: int, config: TransformerConfig, **kwargs):
+        self.config = config
+        super().__init__(
+            input_size=input_size,
+            output_size=output_size,
+            config=self.config,
+            parallel_mode="row",
+            **kwargs,
+        )
+
+
+class TEDotProductAttention(te.pytorch.DotProductAttention):
+    """
+    Wrapper for the Transformer-Engine's `DotProductAttention` layer that also
+    has "flash attention" enabled.
+
+    Note that if Megatron's parallel_state has not been initialized
+    yet, the tp_group passed to TE will be None and must be set later
+    via set_tensor_parallel_group().
+    """
+
+    def __init__(
+        self,
+        config: TransformerConfig,
+        layer_number: int = 1,
+        attn_mask_type: AttnMaskType = AttnMaskType.padding,
+        **kwargs
+    ):
+        self.config = config
+        super().__init__(
+            num_attention_heads=self.config.num_attention_heads,
+            kv_channels=self.config.kv_channels,
+            attention_dropout=self.config.attention_dropout,
+            layer_number=layer_number,
+            attn_mask_type=attn_mask_type.name,
+            sequence_parallel=self.config.sequence_parallel,
+            tp_size=self.config.tensor_model_parallel_size,
+            get_rng_state_tracker=get_cuda_rng_tracker,
+            tp_group=get_tensor_model_parallel_group(check_initialized=False),
+            **kwargs,
+        )

megatron/core/transformer/dot_product_attention.py

+# Copyright (c) 2023, NVIDIA CORPORATION. All rights reserved.
+
+
+import math
+
+import torch
+from torch import Tensor
+
+from megatron.core import parallel_state, tensor_parallel
+from megatron.core.fusions.fused_softmax import FusedScaleMaskSoftmax
+from megatron.core.transformer.enums import AttnMaskType
+from megatron.core.transformer.module import MegatronModule
+from megatron.core.transformer.transformer_config import TransformerConfig
+from megatron.core.transformer.utils import attention_mask_func
+from megatron.core.utils import divide
+
+
+class DotProductAttention(MegatronModule):
+    """
+    Region where selective activation recomputation is applied.
+    This region is memory intensive but less compute intensive which
+    makes activation checkpointing more efficient for LLMs (20B+).
+    See Reducing Activation Recomputation in Large Transformer Models: https://arxiv.org/abs/2205.05198 for more details.
+
+    We use the following notation:
+     h: hidden size
+     n: number of attention heads
+     p: number of tensor model parallel partitions
+     b: batch size
+     s: sequence length
+    """
+
+    def __init__(
+        self, config: TransformerConfig, layer_number: int = 1, attn_mask_type=AttnMaskType.padding
+    ):
+        super().__init__(config=config)
+
+        self.config: TransformerConfig = config
+
+        self.layer_number = max(1, layer_number)
+        self.attn_mask_type = attn_mask_type
+
+        projection_size = self.config.kv_channels * config.num_attention_heads
+
+        # Per attention head and per partition values.
+        world_size = parallel_state.get_tensor_model_parallel_world_size()
+        self.hidden_size_per_partition = divide(projection_size, world_size)
+        self.hidden_size_per_attention_head = divide(projection_size, config.num_attention_heads)
+        self.num_attention_heads_per_partition = divide(config.num_attention_heads, world_size)
+
+        coeff = None
+        self.norm_factor = math.sqrt(self.hidden_size_per_attention_head)
+        if self.config.apply_query_key_layer_scaling:
+            coeff = self.layer_number
+            self.norm_factor *= coeff
+
+        self.scale_mask_softmax = FusedScaleMaskSoftmax(
+            input_in_fp16=self.config.fp16,
+            input_in_bf16=self.config.bf16,
+            attn_mask_type=self.attn_mask_type,
+            scaled_masked_softmax_fusion=self.config.masked_softmax_fusion,
+            mask_func=attention_mask_func,
+            softmax_in_fp32=self.config.attention_softmax_in_fp32,
+            scale=coeff,
+        )
+
+        # Dropout. Note that for a single iteration, this layer will generate
+        # different outputs on different number of parallel partitions but
+        # on average it should not be partition dependent.
+        self.attention_dropout = torch.nn.Dropout(self.config.attention_dropout)
+
+    def forward(
+        self, query_layer: Tensor, key_layer: Tensor, value_layer: Tensor, attention_mask: Tensor
+    ):
+
+        # ===================================
+        # Raw attention scores. [b, n/p, s, s]
+        # ===================================
+
+        # [b, np, sq, sk]
+        output_size = (
+            query_layer.size(1),
+            query_layer.size(2),
+            query_layer.size(0),
+            key_layer.size(0),
+        )
+
+        # [sq, b, np, hn] -> [sq, b * np, hn]
+        # This will be a simple view when doing normal attention, but in group query attention
+        # the key and value tensors are repeated to match the queries so you can't use simple strides
+        # to extract the queries.
+        query_layer = query_layer.reshape(output_size[2], output_size[0] * output_size[1], -1)
+        # [sk, b, np, hn] -> [sk, b * np, hn]
+        key_layer = key_layer.view(output_size[3], output_size[0] * output_size[1], -1)
+
+        # preallocting input tensor: [b * np, sq, sk]
+        matmul_input_buffer = parallel_state.get_global_memory_buffer().get_tensor(
+            (output_size[0] * output_size[1], output_size[2], output_size[3]),
+            query_layer.dtype,
+            "mpu",
+        )
+
+        # Raw attention scores. [b * np, sq, sk]
+        matmul_result = torch.baddbmm(
+            matmul_input_buffer,
+            query_layer.transpose(0, 1),  # [b * np, sq, hn]
+            key_layer.transpose(0, 1).transpose(1, 2),  # [b * np, hn, sk]
+            beta=0.0,
+            alpha=(1.0 / self.norm_factor),
+        )
+
+        # change view to [b, np, sq, sk]
+        attention_scores = matmul_result.view(*output_size)
+
+        # ===========================
+        # Attention probs and dropout
+        # ===========================
+
+        # attention scores and attention mask [b, np, sq, sk]
+        attention_probs: Tensor = self.scale_mask_softmax(attention_scores, attention_mask)
+
+        # This is actually dropping out entire tokens to attend to, which might
+        # seem a bit unusual, but is taken from the original Transformer paper.
+
+        if not self.config.sequence_parallel:
+            with tensor_parallel.get_cuda_rng_tracker().fork():
+                attention_probs = self.attention_dropout(attention_probs)
+        else:
+            attention_probs = self.attention_dropout(attention_probs)
+
+        # =========================
+        # Context layer. [sq, b, hp]
+        # =========================
+
+        # value_layer -> context layer.
+        # [sk, b, np, hn] --> [b, np, sq, hn]
+
+        # context layer shape: [b, np, sq, hn]
+        output_size = (
+            value_layer.size(1),
+            value_layer.size(2),
+            query_layer.size(0),
+            value_layer.size(3),
+        )
+
+        # change view [sk, b * np, hn]
+        value_layer = value_layer.view(value_layer.size(0), output_size[0] * output_size[1], -1)
+
+        # change view [b * np, sq, sk]
+        attention_probs = attention_probs.view(output_size[0] * output_size[1], output_size[2], -1)
+
+        # matmul: [b * np, sq, hn]
+        context_layer = torch.bmm(attention_probs, value_layer.transpose(0, 1))
+
+        # change view [b, np, sq, hn]
+        context_layer = context_layer.view(*output_size)
+
+        # [b, np, sq, hn] --> [sq, b, np, hn]
+        context_layer = context_layer.permute(2, 0, 1, 3).contiguous()
+
+        # [sq, b, np, hn] --> [sq, b, hp]
+        new_context_layer_shape = context_layer.size()[:-2] + (self.hidden_size_per_partition,)
+        context_layer = context_layer.view(*new_context_layer_shape)
+
+        return context_layer

megatron/core/transformer/enums.py

+# Copyright (c) 2022, NVIDIA CORPORATION. All rights reserved.
+
+import enum
+
+
+# can we get rid of this?
+# it's being used in pipeline schedules
+class ModelType(enum.Enum):
+    encoder_or_decoder = 1
+    encoder_and_decoder = 2
+
+
+# class LayerType(enum.Enum):
+#     encoder = 1
+#     decoder = 2
+
+
+class AttnType(enum.Enum):
+    self_attn = 1
+    cross_attn = 2
+
+
+class AttnMaskType(enum.Enum):
+    padding = 1
+    causal = 2

megatron/core/transformer/identity_op.py

+# Copyright (c) 2023, NVIDIA CORPORATION. All rights reserved.
+import torch
+
+
+class IdentityOp(torch.nn.Module):
+    """
+    This is a placeholder for IdentityOp (NoOp)
+    """
+
+    def __init__(self, *args, **kwargs):
+        super(IdentityOp, self).__init__()
+
+    def forward(self, x, *args, **kwargs):
+        return x

megatron/core/transformer/mlp.py

+# Copyright (c) 2023, NVIDIA CORPORATION. All rights reserved.
+
+import torch
+import torch.nn.functional as F
+
+from megatron.core import tensor_parallel
+from megatron.core.fusions.fused_bias_gelu import bias_gelu_impl
+from megatron.core.transformer.custom_layers.transformer_engine import (
+    TELayerNormColumnParallelLinear,
+    TERowParallelLinear,
+)
+from megatron.core.transformer.module import MegatronModule
+from megatron.core.transformer.transformer_config import TransformerConfig
+
+
+class MLP(MegatronModule):
+    """
+    MLP will take the input with h hidden state, project it to 4*h
+    hidden dimension, perform nonlinear transformation, and project the
+    state back into h hidden dimension.
+
+
+    Returns an output and a bias to be added to the output.
+    If config.add_bias_linear is False, the bias returned is None.
+
+    We use the following notation:
+     h: hidden size
+     p: number of tensor model parallel partitions
+     b: batch size
+     s: sequence length
+    """
+
+    def __init__(self, config: TransformerConfig):
+        super().__init__(config=config)
+
+        self.config: TransformerConfig = config
+
+        # If this is a gated linear unit we double the output width, see https://arxiv.org/pdf/2002.05202.pdf
+        ffn_hidden_size = self.config.ffn_hidden_size
+        if self.config.gated_linear_unit:
+            ffn_hidden_size *= 2
+
+        self.linear_fc1 = TELayerNormColumnParallelLinear(
+            self.config.hidden_size,
+            ffn_hidden_size,
+            config=self.config,
+            init_method=self.config.init_method,
+            bias=self.config.add_bias_linear,
+            skip_bias_add=True,
+        )
+
+        if self.config.gated_linear_unit:
+
+            def glu(x):
+                x = torch.chunk(x, 2, dim=-1)
+                return self.config.activation_func(x[0]) * x[1]
+
+            self.activation_func = glu
+        else:
+            self.activation_func = self.config.activation_func
+
+        self.linear_fc2 = TERowParallelLinear(
+            self.config.ffn_hidden_size,
+            self.config.hidden_size,
+            config=self.config,
+            init_method=self.config.output_layer_init_method,
+            bias=self.config.add_bias_linear,
+            skip_bias_add=True,
+        )
+
+    def forward(self, hidden_states):
+
+        # [s, b, 4 * h/p]
+        intermediate_parallel, bias_parallel = self.linear_fc1(hidden_states)
+
+        if self.config.bias_gelu_fusion:
+            assert self.config.add_bias_linear is True
+            assert self.activation_func == F.gelu
+            intermediate_parallel = bias_gelu_impl(intermediate_parallel, bias_parallel)
+        else:
+            if bias_parallel is not None:
+                intermediate_parallel = intermediate_parallel + bias_parallel
+            intermediate_parallel = self.activation_func(intermediate_parallel)
+
+        # [s, b, h]
+        output, output_bias = self.linear_fc2(intermediate_parallel)
+        return output, output_bias